Abstract: The steam turbine thermal capability correction curve is an important input of unit performance test,and the accuracy of the curve directly affects the reasonable valuation of the final power of the unit.This paper collected operational data of several nuclear power units of one supplier and applied the steam turbine heat balance method to check and analyze the correcting curves.Results showed that the power back-pressure characteristic curve and the main steam pressure correction curve deviate greatly from the actual values,the influence degree of the power back-pressure characteristic curve on the test results is related to the test back-pressure value.The closer to the design value of the test back-pressure,the smaller the correction deviation.The deviation of the main steam pressure correction curve for power correction is about 3 MW,and it reaches 5 MW or more at the beginning of the cycle.The analysis results of this paper can provide reference for the examination of the correction curves,performance test examination and the valuation of the test results for nuclear power plant.