Gas drilling has been widely applied because of its enormous advantage in protecting gas field, improving drilling rate, etc. However, the issue of hole deviation has not been appropriately solved, it still restricts the development of gas drilling. At present the study on gas drilling in terms of borehole deviation mechanism and control method is very few and has not form a theory of large scale systems at home and aboard. According to some examples of gas drilling in Daqing Oilfield, this text analyze of the reasons for deviation of gas drilling from many aspects such as geological factor, borehole diameter expanding, drilling parameter, hole drift angle, circulation medium of drilling, etc. Base on the analytic result and the site example of drilling, tentative diagnosis measures has been given to gas drilling control measures, this result laid a solid foundation for the design and construction of gas drilling.