There are a lot of mountains and hills in the Southern China, and the fields are small with dispersed height. It makes the work environment unfit for a large-size combined harvester. In order to adapt to the bad working situation and improve the operation quality and efficiency of the mechanized harvesting in south of China, a 4LZ–0.8 type mini rice combined harvester was designed with small low loss rate and high clean efficiency. The parameter of key components, such as the walking device, the threshing and separating installation, the cleaning system and second cutter were analyzed and confirmed. A experiment has been done to test the performance. The results shows that the production rate was 0.116 hm2/h, the impurity rate was 1.8%,the broken rate was 0.2%, and the total loss rate was 2.0%. All of the parameters were better than those of industrial and local standards.