In a pressurized water reactor nuclear power plant, the compression force of the fuel assembly, coolant flow, radiation creep, burnup and other factors will cause the bowing of the fuel assembly. The bowing of the fuel assembly affects the distribution of the water gap between the assemblies. It affects the slowing behavior of neutrons and the heat transfer performance of the core, which in turn affects the operating parameters of the reactor core. This paper discusses the cause and mechanism, influence and consequences of assembly bowing (including the influence on core power distribution, core radial power tilt, nuclear enthalpy rise hot channel factor, heat flux hot channel factor and other parameters), and uses Monte Carlo software JMCT to verify the correctness of the calculation program of component bowing PCM. Finally, through the deterministic calculation program, a simulation analysis of the assemblies bowing of the CPR1000 nuclear power plant is carried out. The calculation results show that: at certain fuel consumption, as the water gap increases or decreases, the fuel assembly power will increase or decrease, the power distribution of the core will tilt, affecting the safe operation of nuclear power plants.