There is great temperature gradient in the absorber of the high energy laser energy meter for a long time, which results in great difficulties in measuring the real temperature of the absorber. In this situation, the accuracy of the energy meter is affected by the heat specific of the material, the responsibility of the temperature sensors and the heat loss. The temperature field of the absorber is simulated, and then a method that multiple discrete thermocouple sensors are used to measure the temperature rise of absorbers is introduced. The average temperature of each small segment in the absorber can be exactly obtained by controlling the distance of the adjacent thermocouples and the depth of the thermocouples, so as to calibrate the heat specific and the responsibility of the temperature sensors. The measurements are taken to decrease the rate of the heat loss and the heat loss can also be calibrated after obtaining the real temperature distribution and the time of the thermal equilibrium. The research on the absorption coefficient is facilitated with the ray tracing method. The absorption coefficients with the parameters of the real beams and the real absorption cavity are calculated and the measurement results are calibrated. According to the uncertainty of the each process, the estimate of the measurement uncertainty of the laser energy meter is 5.8％ (k=2), and the rationality of the measurement uncertainty is verified with the comparison method.