Objective To investigate the status and present problems of standardization of outpatient and emergency diagnosis information of a hospital, and discuss the room of improvement. Methods The outpatient and emergency diagnosis information of a tertiary hospital was retrieved, and the data were inspected using tracking method over the whole process from diagnostic information input to data maintenance, for analysis of causes of the nonstandard diagnosis. Results The standard rate of the outpatient and emergency diagnosis of the hospital was 51. 07％ (15278/29915). Statistics by the departments visited found the traditional Chinese medicine department with the most nonstandard diagnosis;that by diagnosis names found the most nonstandard diagnosis in such common diseases as hypertension and diabetes. These nonstandard diagnosis may be contributed mainly to the system, the standard dictionary, the doctor and the imperfect maintenance mechanism. Conclusions It is suggested to improve the system maintenance mechanism, streamline the maintenance process, and train the doctors in dictionary use and input, to improve the outpatient and emergency diagnostic information standardization.