The lubricating medium used in the friction pair of thrust bearing of nuclear main pump has low viscosity,and the bearing works under extreme working conditions such as high temperature and high pressure.When using ultrasonic technology to accurately measure the distribution of the lubrication film,the influence of environmental factors should be considered.An ultrasonic testing model of the lubrication film distribution of thrust bearing was established,and a actual measurement of thrust lubrication state was conducted on a simulation test bench.In the analysis of the test results,the influence of environmental factors such as temperature and pressure during the measurement was considered,and the degree of influence of environmental factors on the accuracy of ultrasonic testing was analyzed.The results show that the thrust bearing is in the boundary lubrication state during the start and stop stages,and the lubrication film thickness value is increased by 38.5% when considering the influence of temperature and pressure.The thrust bearing is in a fluid lubrication state at the rated speed,and the lubrication film thickness value is increased by 39.8% when the influence of temperature and pressure is considered.