Abstract: At present, the system of high pressure water jet punching with low flow, low pressure and small caliber is limited and ineffective. To promote this system widely applied to outburst prevention measures in underground, the experiments which worked on choosing and optimizing the caliber and punching angle of high pressure water jet have been done in Qianjiaying No.5 Coal Mine of Kailuan Group. It has obtained the data of on-way resistance loss and local resistance loss by theoretical derivation. The analytic curve based on MATLAB numerical analysis method got the optimal punching gun caliber. According to the theoretical results, it achieved the range of field test parameters and optimal field test parameters of high pressure water jet caliber. The results indicate that 6 mm caliber is most effective when the pumping pressure is up to the rated maximum value of 31.5 MPa. According to the comparison between theoretical and field test, the experiments were carried out in choosing the punching angle. Based on the gray comprehensive evaluation, the punching scheme was predicted and evaluated. The results show that the optimal punching angle of heading face is raging from 5° to 10°. In addition, the volume of coal discharge is 1.2 to 1.5 times compared with the punching angle of 0°. The stope face adopts an angle of 10° between center hole and horizontal plane, an angle 5° between bilateral holes and horizontal plane and horizontal angle 30° between two adjacent holes. The influencing factor, gray relational degree is equal to 0.960 91.