Overbuying a stock is called overbought. KDJ stochastic theory originated from the futures market and was invented by George Lan. It belongs to the overbought and oversold index that fluctuates between 0- 100, and consists of three curves, K, D and J. In practical application, the value of KD is taken. The value range of KD is 0- 100, which is divided into: above 80, the closing price of overbought area is too low, below 20, the closing price of overbought area is too high, and the rest are wandering areas.