In the procedure of digital design of machinery system based on case-based reasoning (CBR), retrieval strategy and method of case had decisive influence on validity and reliability of retrieve. Combined with object-oriented case representation approach, determination method for resemblance level of machinery parts characteristics during case retrieval procedure was analyzed, fuzzy mathematics and grey relational analysis methods were introduced into calculation of resemblance level of characteristics properties. Combination weight for characteristic properties of the machinery parts was determined through hierarchy analysis process and deviation information method based on similarity values. The case retrieval calculation method had high discernment and verified successfully through design procedure of spade punch planter.