Aiming at the problems that the length of lifting chain, jitter separation ability and separation effect of the mixture of potatoes were not matched, the new type of lifting chain device of potato digger under the condition of heavy soil was designed. Based on the theoretical analysis of the separation, deliver and disintegration of the mixture and the mixture of potato and soil on the lifting chain, the main factors influenced the separation effect of the dispersion and crushing were obtained, and the range of lifting chain length and structure parameters of jitter that affected the process of transportation was got. The combination design of orthogonal and quadratic regression equation for the flail was adopted. Taking the length of the second elevator chain, forward speed of machine and velocity of lifting chain as the experimental factors, the field experiment was carried out to test the obvious potato rate and the injured potato rate. The test was implemented in agricultural sciences of academy in Heilongjiang Province at the beginning of September, 2016. The experimental data was processed and optimized by software Design-Expert 8.0.6. The importance of main factors affecting obvious rate was the second elevator chain length and the forward speed of machine. The importance of main factors affecting injury rate was the second elevator chain length, the forward speed of machine and the velocity of the lift chain. Test results showed that when the second elevator chain length was 3.1m, the forward speed of machine was 1.2m/s, lifting chain line speed was 1.5m/s, the obvious potato rate was 98.1%, and the injured potato rate was 1.1%. The function of machine was fully suitable for the potato excavator harvesting requirements. The relationship between the structure and position of jitter on digger, the installation position of the jitter, and the effects of separation and dripped of potato that suited the condition of heavy soil was determined. The research provided an important theoretical support and reference for the improvements and optimization of the lifting chain conveyor separation parts on potato digger.