Morphological associative memory is made up by replacing the sum of input signals by maximum or minimum operation. Ritter presented a procedure of associative memory, which utilizes associative memory matrix M and W sophisticatedly. This paper treats the recalling rate of associative memory. At first, conditions of perfect recalling are given. Then the perfect recalling rate of associative memory is derived based on these conditions. The formula of perfect recalling rate found out to be equal to the perfect recalling rate obtained by experiments.