The condenser of Pressurized Water Reactor (PWR) nuclear power plant in China has many cooling tube leakage events, resulting in serious safety impact and economic loss. One of the main reasons is the fluidelastic instability caused by the large support plate spacing in half side operation. The corresponding calculation model is not given in the design specifications. Combined with the basic theory of cooling pipe vibration and comprehensively comparing different support plate spacing design and calculation methods, the mathematical model used in support plate spacing calculation in Heat Exchange Institute (HEI) standards is deduced. On this basis, the support plate spacing calculation model of condenser half side operation in PWR nuclear power plant is proposed. Based on a pressurized water reactor nuclear power project, the calculation and verification are carried out under four working conditions: Turbine Maximum Continuous Rating condition (TMCR), Winter Continuous Rating condition (WCR), Winter condenser half side operation condition (WHS) and Winter load shedding condition (WLS). In this project, the support plate spacing under winter condenser half side operation condition was 663.67mm, which is the most dangerous working condition under four working conditions. It is suggested that the final conservative support plate spacing should be determined according to the most stringent working conditions in the condenser support plate spacing design of nuclear power plant. Using the evaluation models of Alstom and Westhouse, the condenser support plate spacing of the PWR nuclear power plant project is checked and verified. The support plate spacing obtained by the mathematical model is relatively conservative and safe. The physical meaning of this method is clear and easy to use. It has certain guiding significance for the support plate spacing design of condensers in PWR nuclear power plants in China.