AIM:To observe the efficacy and safety of trabeculectomy in the primary acute angle-closure glaucoma by ultrasound biomicroscopy. METHODS:Eighty cases 80 eyes of primary acute angleclosure glaucoma,which received trabeculectomy,were divided into 2 groups by the preoperational intraocular pressure(IOP) value,the high IOP group:30 cases 30 eyes,IOP≥30mmHg,the control group:50 cases 50 eyes, IOP<30mmHg.And after surgery,routine examinations such as IOP,visual acuity and ultrasound biomicroscopy (UBM) were observed and analyzed. RESULTS:Most patients of high IOP group gained a better vision.The IOP of both groups were controlled between 8 to 15mmHg after surgery.In high IOP group, cyclodialysis was observed in 1 case,malignant glaucoma was observed in 1 case and shallow anterior chamber was observed in 1 case.Shallow anterior chamber was observed in 1 case of the control group.Anterior chamber depth(ACD),angle opening distance(AOD) and trabecular-ciliary process distance(TCPD) after operation compared with the preoperative had no significant differences. CONCLUSION:Trabeculectomy for AACG with persistent high IOP is safe and effective.Trabeculectomy should be performed promptly after using adequate remedies.UBM can find cyclodialysis,malignant glaucoma and shallow anterior chamber after trabeculectomy.UBM plays an important role in the treatment of acute angle-closure glaucoma.