Abstract: Given the challenges faced by in-situ pyrolysis of tar-rich coal, such as high ground stress, complex geological conditions, and difficult analysis of pyrolysis products, a high-temperature triaxial test device was designed and built independently to simulate the in-situ pyrolysis process of tar-rich coal. The test device includes a high-temperature and high-pressure gas supply module, an in-situ pyrolysis module, a servo control module, and a product separation and cooling module. Taking the Shenfu tar-rich coal in Northern Shaanxi Province as the research object, the pyrolysis experiments of high temperature and high stress under different burial depths were simulated based on the high-temperature triaxial test device. The results show that the high-temperature triaxial apparatus can provide axial compression of 0～15 MPa （buried depth of 0～600 m）. The loading response is rapid, and the stress can remain stable during pyrolysis. During the experiment, the high-temperature triaxial apparatus can heat the central temperature of coal samples over 600 ℃, and can realize the pyrolysis experiment of tar-rich coal at the set temperature. When the simulated burial depth increased from 100 m to 300 m, the axial stress on coal samples increased from 2.45 MPa to 7.35 MPa, the yield of pyrolysis semi-coke risen from 67.70% to 68.04%, and the tar yield first increased and then decreased, with the highest value of 6.50%. With the increase of simulated burial depth, the contents of light oil and phenol oil in tar gradually increased from 19% and 9.5% to 25% and 12% respectively. The proportion of pitch in tar is reduced from 25% to 20%; The aromatic hydrocarbon content increased from 32% to 38%, and the aliphatic hydrocarbon content decreased from 28.5% to 19.3%. The permeability of coal seam decreases with the increase of stress, which hinders the heat and mass transfer in the pyrolysis process, leading to the increase of residence time of pyrolysis products of tar-rich coal, the secondary reaction of tar, the fracture of long-chain aliphatic hydrocarbon compounds and the transformation of methyl and methylene into small molecular compounds. On the other hand, stress promotes the condensation reaction of tar molecules and the content of polycyclic aromatic hydrocarbons increases rapidly. The increase of in-situ stress improves the yield of light aromatics and coke, and the quality of tar is improved to light weight.