Based on the large gas content in 3311 working face of Hexi Mine, in order to make sure the safe mining, drilling pre-drainage was needed. To design reasonable spacing drilling, numerical simulation and field test were applied to verify, the result showed that effective radius of single drilling by two methods all came 1.6 m, considering superposition effect, 2.5 times single drilling effective radius in multiple drilling, the drainage result met the needs, providing technical reference for similar mines.