Recently, while watching the market, I recalled an old topic— the KDJ indicator. To be honest, this thing is quite well-known in the retail trader community, many treat it as a trading bible, but actually not that many people use it well.

Over the years of observing the market, I feel it’s necessary to have a good discussion about what exactly KDJ is and how to truly utilize it.

The KDJ indicator is essentially a stochastic indicator, with the core idea of comparing the closing price’s position within a certain period’s price range to determine if the market is overbought or oversold. On the chart, you will see three lines—K line (fast line), D line (slow line), and J line (direction line). The K and D lines mainly indicate overbought and oversold conditions, while the J line reflects the deviation between K and D lines.

The most basic method is to look for golden crosses and death crosses. When the K line crosses above the D line, especially a low-level golden cross formed below 20, it usually signals a buying opportunity; conversely, when the K line crosses below the D line, especially a high-level death cross formed above 80, it signals a selling opportunity. It sounds simple, but in actual trading, catching these points requires experience.

Besides golden and death crosses, divergence phenomena are also worth paying attention to. When the stock price makes lower lows but the KDJ indicator makes higher lows, this is a bullish divergence, often indicating an imminent reversal. Conversely, if the stock price hits new highs but the KDJ indicator weakens, it’s a bearish divergence, warning of a potential decline. I remember vividly the Hang Seng Index in 2016—during a clear bullish divergence at the bottom, smart traders bottom-fished and later made substantial profits.

The KDJ indicator also has pattern judgments like double bottoms and double tops. When KDJ moves below 50 and forms a W bottom, it suggests a possible reversal upward; on the other hand, when it forms an M top above 80, it warns of a potential decline.

However, honestly, KDJ is not foolproof. The biggest problem is that it can generate false signals, especially in choppy markets, often giving early buy or sell signals that lead to frequent entries and exits, resulting in losses. Also, its signals tend to lag, which can be problematic in fast-moving markets. Most importantly, you shouldn’t rely solely on KDJ; it must be combined with other indicators, candlestick patterns, volume, and multiple dimensions for comprehensive analysis.

My advice is to treat KDJ as an auxiliary tool, used together with trend analysis and support/resistance levels. In clear uptrends or downtrends, KDJ tends to perform more steadily and reliably. But during sideways consolidation, it’s better to reduce the weight of its signals and look for confirmation from other indicators.

True trading masters never rely blindly on a single indicator, and KDJ is no exception. The key is to continuously accumulate experience in practice, knowing when to trust it and when to be cautious of it. Only then can you maximize its advantages and avoid its pitfalls.