Objective To evaluate Chinese medicine constitution scale using item response theory. Methods The answer situation of 1114 cases of tested Chinese medicine constitution scales was made item parameter estimation by the grade reaction model guided by item response theory. The item characteristic curves of the items were drawn.Results Discrimination parameters of other items were more than 0. 60 except item 53. The items seemed to have good separating capacity for subjects of different abilities. Difficulty parameters of about half items were between- 3. 00 and 3. 00. The difficulty was moderate. Difficulty parameters of partial items were slightly large. The item characteristic curves had a tendency to right. Conclusion After item response theory analysis

the overall performance of Chinese medicine constitution scale seemed good. Partial items had the problems of low discrimination and large difficulty. The scale needed to be revised by further discussion.