The invention relates to and particularly discloses a method for improving measuring precision of a thermal resistance thermometer. The method comprises the following steps that 1, m points are selected within the measuring range of one thermal resistance thermometer as temperature correction datum points, and the output temperature value of the nth datum point is Yn; 2, the resistance value Rn of the nth temperature correction datum point is collected according to the data table of the thermal resistance thermometer; 3, an input temperature value Xn corresponding to the nth temperature correction datum point is acquired; 4, m-1 temperature intervals are formed by the m temperature correction datum points, and when a temperature value Ti measured by the thermal resistance thermometer is within the ith temperature interval, the gain Ai and polarization Bi of the ith temperature interval are obtained according to the step 3; 5, the temperature value Ti measured by the thermal resistance thermometer is calibrated and corrected, and a calibrated and corrected temperature value Ti' is obtained. According to the method, the measuring precision of the thermal resistance thermometer of a nuclear power plant is improved, the error of a whole temperature measuring channel is lowered, and the safety and economical efficiency of the power plant are improved.