Strong feedback phenomenon between the reactor physical and thermal-hydraulic has an important impact on the design and safety analysis of pressured water reactor (PWR). In order to accurately simulate the strong coupling effect of hydraulic in PWR, a reactor multiphysical coupling calculation code is developed, in which the three-dimensional (3D) space–time neutron dynamic equation is solved by the nodal expansion method (NEM) and nodal green's function method (NGFM); the coolant temperature and fuel temperature are solved by single channel model and the cylinder heat conduction model, respectively. The 3D light water reactor (LWR) benchmark and the Nuclear Energy Agency Committee on Reactor Physics (NEACRP) PWR rod ejection benchmark are used to verify the neutronics model and coupling calculation solution ability, respectively. The results show that: (1) the NEM and NGFM have high accuracy in solving the 3D space–time neutron dynamics equation; (2) the results of neutronics and thermal-hydraulic coupling steady/transient calculation such as core normalized power and fuel Doppler temperature are in good agreement with those of the NEACRP PWR benchmark, and the calculation accuracy is equivalent to similar software. Four coupled reactor physics and thermal hydraulic calculation modes are used to analyze the influence of different reactor physics calculation methods and thermal hydraulic calculation methods on the key parameters of PWR transient process in this paper. The results show that the mode of NGFM + finite volume method (FVM) can more accurately simulate the reactor core normalized power peak and fuel Doppler temperature.