In order to solve the problems of ambiguous separating mechanism of swing separation sieve and the obvious contradiction between the obvious performance and the abrasion performance caused by the improper match of operation parameters, high speed camera was used to capture the distribution of mixture of potato and soil of different crank rotational speed, the screen surface inclination and the machine forward speed. The variation of the distribution height of potato-soil mixture was counted and analyzed, and the separation mechanism was revealed based on these counted results. Finally, the experimental value range of the main factors which affected the separation performance of swing separation sieve was obtained. The rate of obvious and abrasion were used as the evaluation index to establish the regression mathematical model between the indexes and the factors by applying Box-Behnken response surface test method, thus optimizing the structure and working parameters which affected the separation performance of the swing separation sieve. The results showed that the primary and secondary order of the effect of factors on obvious rate and abrasion rate were crank rotational speed, screen surface inclination and machine forward speed. The crank rotational speed of 230r/min, screen surface inclination of 19.42° and machine forward speed of 2.04km/h were the best combination factors, the obvious rate and abrasion rate were 99.4% and 0.002%, respectively after optimizing. According to the limitation of operating parameters, the best parameters were adjusted as follows: when the crank rotational speed was 230r/min, screen surface inclination was 21.1° and machine forward speed was 2.03km/h, the obvious rate was 98.94% and the abrasion rate was 0.21%， the obvious rate was increased by 1.68 percentage points, and the abrasion rate was decreased by 9.6 percentage points compared with that before optimization. The results of parameter optimization were better than the national standard.