In order to address the challenges of domestically-made large-diameter high-pressure quick-opening closure in LNG receiving station, this paper compared the results of electrical stress measurement test and finite element analysis on PN15 MPa DN1 300 mm pressure ring-type quick-opening closure. The results validated the accuracy of finite element model. The stress classification method and elastic-plastic analysis method were employed to check the strength of the quick-opening closure. Following this, the thickness of the head cover of the quick-opening closure was optimized. The results showed that the above mentioned quick-opening closure ensured effective sealing and the strength of each component complied with the requirements. The optimized head cover also met the strength requirements, and this paper offered reference for the future design of large-diameter high-pressure quick-opening closure.