Abstract: Abstract: In view of the current situation that the cleaning sieve of the grain combine harvester is less applicable to soybean cleaning and the field performance test of soybean mechanical harvest is less, field performance tests of cleaning sieve of soybean harvest were conducted. We selected PRO688D as the field performance test machine and suike 20 as the soybean test variety. According to the preliminary experiments, researches of soybean combine harvester, the types and parameters of cleaning sieve which included upper, lower and tail sieve were determined. Selected conventional fish scale sieve, lengthened fish scale sieve, misplaced fish eye sieve, linear fish eye sieve and shell sieve as upper sieve, mesh sieve, round hole sieve and hexagonal hole sieve as lower sieve, and fish scale tail sieve and grid tail sieve as tail sieve. The vertical distance between two adjacent parallel sieves in the fish scale sieve is taken as the sieve plate opening of the fish scale sieve, and they were set as 26 mm, 28 mm and 30 mm. The cleaning loss rate and impurity rate during the field operation of the soybean combine harvester were used as the evaluation indexes of the soybean cleaning operation. Then, the field performance tests of cleaning soybean were carried out, and the data of the field performance test were analyzed and evaluated with the fuzzy comprehensive evaluation method. The optimization of the combination of sieve plate opening of fish scale sieves, upper sieves, lower sieves, tail sieves and cleaning sieves in the applicability of soybean harvesting was completed. The evaluation of cleaning operation level of different sieve plate opening of fish scale sieve showed that the cleaning operation level of fish scale sieve to soybean was the highest when sieve plate opening was 28mm. That is to say, when sieve plate opening was 28mm, the cleaning applicability of fish scale sieve to soybean was the best. The evaluations of the cleaning operation level of different tail sieve, upper sieve, lower sieve and combinations of cleaning sieve were conducted, the results of the cleaning applicability of different cleaning sieve to soybean were as follows: grid tail sieve was better than fish scale tail sieve; shell sieve and hexagonal hole sieve were the upper sieve and lower sieve with the best applicability for soybean machine cleaning. The highest level of cleaning sieves combination was that upper, lower and tail sieve were shell sieve, hexagonal hole sieve and fish scale tail sieve respectively. Cleaning sieve combination has the best cleaning applicability to soybean under the combination of shell sieve, hexagonal hole sieve and fish scale tail sieve. At this time, the cleaning loss rate of field performance test was 2.04%, and the impact rate was 0.53%. The results showed that the application of fuzzy comprehensive evaluation method to comprehensive evaluation of cleaning loss rate and impurity rate of different cleaning sieves and optimization of cleaning operation level could effectively improve the cleaning applicability of grain combine harvester to soybean. This study can provide the practical basis for solving the problem of low applicability of cleaning sieve to soybean, promote the field test and research on reducing cleaning loss rate and impurity rate of soybean combine harvester, and supply references for the research and development of cleaning device for soybean combine harvester.