Abstract: In order to detect of risky formations in advance and in front of the bit during gas drilling, a downhole impact source tool suitable for gas drilling environment was designed. Based on the gas drilling environment, the key structure of the impact source tool was designed. Through the indoor impact test, the vibration-absorbing structure and impact energy of the impact source tool were optimized. The RecurDyn simulation software was used to analyze impact block movements and optimize the parameters of the key structure. The impact resistance of the bottom vibration-absorbing disc and the tensile strength of the limit structure of the transmission rod were simulated to analyze the mechanical properties of the impact source tool. The field operation plan was made and the main advantages of the tool was analyzed. The results showed that polytetrafluoroethylene (PTFE) could significantly attenuate drill collar waves and coda waves, helpful in pinpointing weak reflection wave signals in the time domain. When the impact energy was 50 J, the propagation distance of impact vibration waves was 18.61 m, which could achieve advanced detection of gas drilling. The maximum impact force on PTFE was 1 796.88 N, and its relative deformation was not more than 0.03%. In addition, the weight of bottom hole assembly (BHA) borne by the limit structure of the transmission rod cannot exceed 1 150 kN. As a result, the structural design and mechanical property simulation of the impact tool for advanced detection while drilling for gas drilling could provide a theoretical basis for the development and application of near-bit impact source tools.