The ocular anatomic features, pupil-blocking force, status of angle synechiae closure and positivity of provocative tests were compared between the primary chronic angle closure glaucoma (PCACG) and primary acute angle closure glaucoma (PAACG) by using ultrasonic biometry, computerized anterior ocular segment image processing technique, gonioscopy and provocative tests. The studies showed that the anterior chamber depth of PAACG were shallower than that of PCACG; the pupil-blocking force of PAACG was stronger than that of PCACG; the status of angle synechiae closure of PCACG were mainly creeping synechiac closure; the positivity of mydriasis test was much higher (46.01%) in PCACG than that (6.8%) in PAACG after iridectomy. These facts suggest approximately half of the PCACG cases may be mult-mechanism to contribute to the angle closure besides the mechanism of pupillary block. Therefore, the authors emphasis that the pupillary block must be eliminated as well as the other mechanism for the treatment of PCACG and finally, a criteria of diagnosis and principles of management of PCACG were proposed.