Abstract: For the commonly used explosion-proof TJ-9000 gyro theodolite in coal mine, the gyro orientation measurement is carried out in Huaibei; it testified the stability of the directional edge orientation with TJ-9000 and the stability of the gyro instrument constants during the working time. Combined with retested data with high precision GT3-3 gyro total station, the weighted values can be calculated so as to testify the maximum likelihood based on hypothesis testing method. Referring to this, we can judge the comprehensive and real precision error with TJ-9000.