Cleaning is one of the most important working processes of rice harvester. However, the sieve is often adhered and blocked by rice threshed mixtures in cleaning process. The problem of adhesion and blockage is caused by wet and sticky properties of rice threshed mixtures. In order to solve above problems, the modified cleaning sieve coated with PTFE was designed. Firstly, the reciprocating friction characteristics of rice straw, rice leaves and modified sieve with PTFE coating were tested. The average friction factor between modified sieve with PTFE coating and rice straw was decreased by 32.2%~32.7%, compared with unmodified sieve. The average friction factor between modified sieve with PTFE coating and rice leaves was decreased by 39.1%~40.2%, compared with unmodified sieve. The modified sieve with PTFE coating had good resistance reduction characteristics. Then, the wetting and adhesion properties test of modified sieve with PTFE coating was carried out. The contact angle of modified sieve with PTFE coating was 110.6°, and the contact angle was increased by 26.8%, compared with unmodified sieve. The interface adhesion force between modified sieve with PTFE coating and rice straw was decreased by 62%~67%. The interface adhesion force between modified sieve with PTFE coating and rice leaves was decreased by 63%~65%. Finally, the field cleaning performance test of the modified sieve with PTFE coating was carried out by using rice harvester. When the working amount of rice harvester was 2.0hm2, the mass of adhesion material on modified sieve with PTFE coating was decreased by 67.8% compared with the unmodified sieve, and the adhesion materials were mainly small debris with scattered distribution. The test results showed that the problem of adhesion and blockage of rice threshed mixtures in cleaning process were solved effectively by modified sieve with PTFE coating.