Abstract: Based on gas-solid coupling model of gas extraction using hole drilled along seam, the authors analyzed the factors of form parameters of coal and gas drainage. It showed that permeability was main controlling factors, gas pressure was second and inversely proportional to effective radius, drainage time controlled effective radius heavily, and measuring method of effective radius should establish the relationship with drainage time. The authors provided the measuring methods of effective radius based on residual gas content, established the relationship between effective radius and drainage time, and determined effective radius with the plan of mining-extraction-drainage. Measuring method was more generally applicable and tested in Huoerxinhe coal mine.