Abstract: The initial ground stress of rock mass is the most basic and original data of the mechanical state of crustal formation. It is a fundamental parameter for the stability analysis of surrounding rock and the design of mining and supporting in mining engineering. Compared with other methods of in-situ stress measurement, the stress relief method of hollow inclusion is more accurate and can get 3D stresses by one-time measurement. The theory of in-situ stress measurement by use of hollow inclusion gauge is discussed in detail. The magnitudes and directions of 3D ground stress at four deep sites in Juji Mine are obtained by means of improved (KX-81) hollow inclusion gauge. Through analysis, the basic rules of the in-situ stress distribution in Juji Mine are as follows: each of the principal stresses is compression stress, and no tensile tress is found; the dip angles of the maximum principal stress are all less than 6o, and their orientation angles range from S10oE to S11oW, that is, the maximum principal stress is close to the horizontal and north-south direction, which shows that the regional geo-stress field of Juji Mine is mainly composed of horizontal tectonic stress; stress regression equations indicate that the vertical stress is not more than the weight of top strata in unit area, and that the values of the principal stresses increase with the increase of depth. The measured results are of great importance to the design of deep mining and the security of production.