In view of the shortcomings of the current automatic non-destructive fruit sorting mechanism, based on the system architecture of automatic fruit sorting robot, a control method for the clamping mechanism of automatic fruit sorting robot was proposed, which combined time delay estimation and smooth sliding mode impedance control method.The time delay estimation method was used to obtain the dynamic model of the clamping mechanism of the automatic fruit sorting system, and a smooth sliding mode impedance control method with adaptive rule adjustment was further designed, which was verified by simulation and experiment.The results showed that this method could make the automatic sorting robot clamping structure stable clamping with high precision, the success rate of clamping was 100%, and the damage to string fruit was zero, which was helpful to realize the accurate and fast automatic sorting of string fruit.