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The cleaning sieve is one of the core components of the combine harvester, which screens the threshed mixture through reciprocating motion. Focusing on the lightweight design of the cleaning sieve of the grain combine harvester, which has the problems of overall weight bias and excess strength, based on the dynamics analysis of the cleaning sieve, the natural frequency and structural strength of the cleaning sieve in working condition were analyzed by using the equivalent static method. The maximum equivalent stress position and main stress distribution area were determined. The dynamic response was transformed into static response by using the equivalent static method. By minimizing the compliance and subject to constraints of structural strength and mass response, the topological optimization of the side wall of the cleaning sieve was conducted. Finally, nylon was chosen as a lightweight material for the design of the jitter plate structure. Based on the results of topological optimization, the main structural features were extracted for model reconstruction and dynamic analysis. The results showed that the maximum variation of the first six natural frequencies of the optimized sieve box was 1.68Hz, and the maximum equivalent stress was decreased from 56.59MPa to 52.46MPa, resulting in a reduction of 7.29%. The mass also was decreased from 75kg to 66.85kg, representing a reduction of 10.86%. Based on these results, an experimental platform was built by using the optimized sieve box, and strain tests and durability tests were conducted under actual working conditions. The test results verified that the optimized cleaning sieve met the strength and stiffness requirements for actual operation, effectively improving the working performance of the cleaning sieve.