Recently, I’ve been organizing my years of stock trading notes and found that many people really misuse the KDJ indicator. So I decided to share my practical insights in hopes of helping friends who are still exploring.

Simply put, KDJ is a momentum indicator that originated in the futures market and was later widely applied in the stock market. It calculates the range of the highest, lowest, and closing prices over a period to assess the strength of the stock and identify overbought or oversold conditions. In plain terms, it’s a tool used to catch medium- to short-term trends, with the cycle adjustable; the default is 9 trading days.

In terms of pattern, KDJ consists of three lines, with a golden cross signaling a buy and a death cross signaling a sell. But this is just the basics; actual trading is much more complex. The K and D values generally fluctuate between 0 and 100, with 50 as the dividing line—above 80 indicates overbought, below 20 indicates oversold. The J value is the most sensitive, often exceeding 100 or dropping below 0.

My most commonly used method is the double crossover approach. A single golden cross might be a false signal, but a second golden cross—especially when it appears near 20—is a more reliable buy signal. Conversely, a second death cross near 80 is a clear sell signal. For example, back in the day, Gree Electric had two death crosses near 80, and combined with divergence between KDJ and the stock price, it indeed shifted from an uptrend to a downtrend. An opposite example is Tsingtao Brewery, where after the stock bottomed out, the KDJ rapidly had two golden crosses near 20, leading to a successful bottom fishing.

Another often overlooked technique is rejecting the death cross. Sometimes, the KDJ indicator turns downward to prepare for a death cross, but the cross never actually happens. This indicates that selling pressure has been absorbed and is an invisible buy point. I’ve seen this with Xiongtao Shares—during a pullback, the KDJ was about to form a death cross but didn’t, and combined with MA support, it was a clear entry signal.

Regarding the J value, when it stays above 90 or below 10 for several days, the stock price usually forms a short-term top or bottom. But this should be used together with other signals like divergence; relying solely on J can lead to traps.

A particularly important tip is about high and low level dulling. KDJ is overly sensitive and can become ineffective during extremely strong or weak markets. At such times, don’t rush to buy or sell; wait for a confirmed golden or death cross before acting. I’ve paid the price for this—thinking I could bottom fish at a low point, only to buy in the middle of a rally.

Multi-timeframe analysis is also crucial. For short-term trading, using resonance between intraday, 30-minute, and 60-minute KDJ can help identify entry and exit points—like a 60-minute golden cross followed by a 30-minute golden cross and an intraday death cross. For medium- to long-term trading, look at the monthly and weekly KDJ; ideally, all should be in a golden cross state before entering. The case of New Hope is a good example: the monthly KDJ was always in a golden cross, the weekly KDJ identified the best trading zone, and the daily KDJ was used for swing trading—this approach is the most reliable.

Finally, I must mention two obvious shortcomings of KDJ. One is that it’s not suitable for stocks with very low trading volume—illiquid stocks or those with long-term small fluctuations—since the signals become unreliable. The other is that savvy traders can manipulate KDJ’s sensitivity to deceive retail investors: they might quickly push down the stock to trigger a death cross, causing retail investors to sell, then rapidly lift the price again. In such cases, trend lines should be used to judge; if the price remains above the trend line, it’s likely just a shakeout.

Overall, KDJ is a double-edged sword. When used properly, it can accurately catch bottoms and tops; if misused, it becomes a tool for “harvesting” retail investors. The key is to understand its essence, combine it with other indicators and trend lines for comprehensive judgment, and avoid over-relying on a single metric. Over the years, through trial and error, I’ve mastered various ways to use KDJ effectively.