Abstract: The microbial limit test of clozapine tablets was validated by using the conventional method and medium dilution method. The results showed that the recovery rates of the test bacteria were more than 70% when they were tested by medium dilution method. The controlling bacteria of Escherichia coli had been detected in the test group, and the negative control strains of Staphylococcus aureus had not been detected in the control group. The study showed that the clozapine tablet had weak bacteriostasis, and the medium dilution method could be used in its microbial limit tests.