Petrochemical pressure vessel equipment develops to be large-scale and super large-scale under extreme working conditions such as high temperature and high pressure, which puts forward new demands for the reliability of the pressure vessel. The present paper discusses the fatigue design theory of pressure vessels and analyzes the fatigue design methods of ASME, BS5500 and JB4732. Pressure vessel loads absorbed (pressure, temperature, earthquake, wind, snow, etc.) have significant stochastic dynamic characteristics and coupling characteristics. The random load of the current design is simplified, with a large safety factor in exchange for equipment safety. However, it is difficult to guarantee the rationality and accuracy of the result. With the development of data acquisition, processing and finite element technology, it is inevitable to be based on measured load spectrum and consider the coupling of the random loads to work out fatigue reliability design methods of pressure vessels.