Abstract: In order to study the effect and investment cost of gas drainage by roof long directional boreholes, analysis was carried out in this paper on the gas drainage effect by roof long directional boreholes according to the occurrence conditions of coal seams, the gas drainage requirements and the observation results in 210100 working face in Xinji No.2 Mine, and the comparison was made with other roof gas drainage technologies.The analysis of the site test data showed that under the same gas drainage conditions, the investment cost of using roof long directional boreholes to drain the gas in the working face saved 44.8% and construction period shortened 30.0% as compared to that of gas drainage by high-level roadway; and the investment coat of gas drainage by roof long directional boreholes was slightly less and the construction period shortened 47.5% as compared to that of gas drainage by high-position boreholes. The tests showed that the gas drainage technology by roof long directional boreholes had high costly with price lower.