For the problems of low material utilization, low life of part, and large allowance of forgings in the traditional process of deep hole casing used in a certain model of coal mine tunnel drilling rig, based on the structural characteristics of deep hole casing, a new precision forming process without burrs was developed. Firstly, a high-temperature compression experiment was conducted on 40Cr alloy steel used in deep hole casing by thermal simulation testing machine Gleeble-1500D, and the true stress-true strain curves at different temperatures and strain rates were obtained. Then, they were imported into the numerical simulation software Deform-3D to simulate the precision forming process of deep hole casing, and the punch load, stress field distribution and temperature field distribution during the forming process were obtained. Finally, based on the simulation results and combined with the actual production conditions, a precision forming mold structure for deep hole casing was designed and validated by process experiments. The numerical simulation results show that the peak load of punch during the pre-forging stage is 3920 kN, and it is 6440 kN during the final forging stage. The stress of mold is within the allowable stress range. And the deep hole casing forgings obtained from the process experiment is fully filled, with good dimensional consistency and no forging defects. The metal flow line is distributed along the contour of forgings, which meets the design requirements. The research results indicate that the proposed precision forming process of deep hole casing is feasible and has certain guiding significance for the actual production of such parts.