Abstract: Pre-drilling optimization study of well site and casing program for CBM pinnate horizontal well could ensure rapid drilling and completion in low cost and production in high ratio. Based on the geologic characteristics of southern Qinshui Basin, this paper analyzes the influence factors: points out the influence of broken formation, such as fault, collapse column, especially. Also, this paper gives an optimal casing program after numerical simulation of the angle between main branches, of the angle between main branches and lateral branches, and of spacing between lateral branches. The result has been used in the development of Qinshui CBM field and good results are obtained.