Abstract: Taking a GYROMAT3000 gyro theodolite as experimental object,the experimental program of measuring temperature drift of apparatus constant for gyro theodolite was designed and walking-in high-low temperature test chamber was carried out. The variance analysis of experimental results showed that the temperature drift of apparatus constant of the GYROMAT3000 had no obvious effect on orientation results. Finally,according to the measurement results,the temperature drift curve was ftted by cubic spline,and the suggested values of apparatus constant were given at different temperatures.