Objective:To optimize the formula of mirtazapine orally disintegrating tablets by orthogonal experiment and determine the stability preliminarily. Methods:The formula was optimized by orthogonal experiment based on 4 impacting factors:the amount of mannotil (A), microcrystalline mellulose (B), low substituted hydroxypropyl cellulose (C) and cross-linked polyvinylpyrrolidone ( D) , respectively with 2 indices of disintegration time and dissolution. The release rate of the orally disintegrating tablets and the ref-erence tablets was studied by similarity factors. The stability was respectively studied by high temperature test, high humidity test and photostability test. Results:The optimum formula of the tablets was as follows:the amount of A, B, C and D was 70, 20, 2. 5 and 10 mg, respectively. The f2 for the orally disintegrating tablets and the reference tablets in the dissolution medium was 63. 38. Conclu-sion:The formula is reasonable, the preparation process is feasible and the quality is stable.