Pressure vessel is the key device of the floating production storage and offloading (FPSO) oil and gas processing module. The internal crude oil generates an impact load on the inner wall under the action of the ship rolling motion, resulting in a stress concentration or even cracking on the head, which seriously threatens the safety of offshore oil mining and FPSO workers. Take No. 118 FPSO pressure vessel as an example, the researches are carried out by considering the actual sea states in the South China Sea. The ship motion response equations are established; a dynamic evaluation study is carried out on the safety evaluation and analysis of the key structure of the pressure vessel based on fluent numerical simulation calculations, the results show that the key structure of the pressure vessel safety, and its stress value is positively correlated with sea state level and filling coefficient. The pressure vessel scale model experiment was carried out with an electric six degrees-of-freedom experimental platform, and the change rule of the measured point test was basically consistent with the simulation value, and the numerical error was only 11.804%, which verified the accuracy of the simulation model. The research results provide guidance for FPSO pressure vessel structure design and preventative maintenance, and the test method provides reference for FPSO pressure vessel simulation test and structure design.