Family study is an effective way to identify disease-causing mutations (DCMs) and characterize the clinical phenotype of genetic diseases. In this study we recruited a Chinese primary open-angle glaucoma (POAG) family spanning six generations and consisting 112 individuals, in which 63 were participated in. Targeted exome sequencing on the proband identified a heterozygous mutation (c.752T>C, p.Val251Aal) in MYOC gene. Sanger sequencing performed on all participants found that fourteen family members carried this mutation. Ten (71.4%) of them were diagnosed with POAG, two (14.3%) with ocular hypertension (OHT) and two (14.3%) without manifestations of glaucoma. According to the results of ophthalmic examinations of the family members and their medical history, we found that the Val251Aal mutation was associated with clinical phenotype including intermediate penetrance, high intraocular pressure (IOP), severe visual defects and requirement of surgery.