Objective To analyze the change of content and ratio of isoflavone aglycones in soybeans treated by drying in oven at 50 ℃, 100 ℃ and 150 ℃，microwave heating for 5 minutes and frying to be ripen. Methods Extracting samples in 80 % ethanol with ultrasonic wave. Soybean isoflavones were separated on an Agilent SB-C18 column and gradient eluted with a mobile phase of methanol plus 0.2 % ice acetic acid. Aglycones and β-glycosides were determined by high performance liquid chromatography with ultraviolet-visible detector at 260 nm. Results Two kinds of aglycone (daidzein and genistein) and two kinds of β-glycoside were detected. The content of daidzein increased 1- to 5-folds, and genistein increased 3- to 15-folds when the temperature in oven was increased from 50 ℃ to 150 ℃. The increase of β-glycosides and aglycones in fried soybeans was the most. The result of heating in microwave was the same as drying in oven at 50 ℃. The results for green bean and black bean were similar to soybean. Conclusion Parts of isoflavone glycoside in soybean were transformed into aglycone by heating, and the active components were then increased and more valuable for human nutrition and health.