The invention relates to a method for increasing the acrylonitrile absorptivity, and aims at solving the problems that in the prior art, the absorption water consumption is high, and the concentration of acrylonitrile in absorption liquid is low. According to the technical scheme, the method comprises the steps that gas-phase raw material flow containing the acrylonitrile and the like and liquid-phase raw material flow enter the bottom and the middle of a first absorption tower respectively, tower-top gas-phase material flow III is separated out at the tower top, and absorption liquid V is drained out from the tower bottom of the first absorption tower; the tower-top gas-phase material flow III enters the bottom of a second absorption tower, and after poor water absorption and cold energy recovery are performed in the second absorption tower, gas-phase light components VIII are exhausted from the tower top; tower bottom liquid of the second absorption tower returns to the tower top of the first absorption tower; poor water is input from the top of the first absorption tower and the top of the second absorption tower. Accordingly, the problems are better solved, and the method can be applied to industrial production for preparing acrylonitrile through propylene ammoxidation.