The design process and features of design knowledge of crawler harvester transmission were analyzed comprehensively. Then, the reasoning process suitable for the rapid design of crawler harvester transmission was researched. Taking the instance similarity matching algorithm as the core, the case based reasoning (CBR) was designed. And taking the constructed design knowledge base of crawler harvester transmission as a core, the rule based reasoning (RBR) method was studied. Also the CBR and RBR hybrid reasoning method was designed. On the basis of all these, the inference mechanism of crawler harvester transmission rapid design system was established. Practical applications showed that this reasoning method could better achieve the crawler harvester transmission rapid design and shorten the design cycle.