Base Object Model (BOM) is a modeling standard for facilitating model composition and reuse. For the problem of conceptual model reuse, similarity between two conceptual models was presented to describe their similar degree. A similarity evaluation algorithm for computing the similarity between two conceptual models was also presented. According to the definition of conceptual model, similarity evaluation of algorithm was induced into two basis processes: name similarity computing and optimization matching computing. How different combinations of interface weighted parameter and behavior weighted parameter of the algorithm to affect the precision and recall was also studied. JC3IEDM was applied as benchmark to evaluate the algorithm. The result reveals that the similar degree of elements and structure between two conceptual models can be represented by their similarity collect. Similarity between two models can be computed by the algorithm. When the recall of algorithm is 100%, the precision is greater than 75%.