As the theoretical foundation of fuzzy control, fuzzy reasoning has been extensively studied. This paper is devoted to the discussion of the similarity property of similarity-based fuzzy reasoning method, triple I fuzzy reasoning method and fuzzy similarity inference method. The similarity degrees between the inferred conclusions of these fuzzy reasoning methods and the consequent part of fuzzy inference rules are analyzed and evaluated. Based on these similarity degrees, the monotonicity, the reversibility and the approximation property of these fuzzy reasoning methods are examined.