The deviation of borehole trajectory leads to the extraction blind zone easily， which seriously threatens the safety and efficient mining of coal mines. Through the analysis of geological， technical and process factors， the root cause of borehole deflection is obtained. This paper analyzes and summarizes the principle and applicability of the existing straight drilling technology. Borehole straightness is a factor that affects the drilling quality. However， the current straight drilling technology has more or less some technical problems and cannot be widely used in coal mines. Therefore， continuous progress should be made on straight drilling so as to develop a kind of straight drilling technology with strong adaptability and easy field application. The in-depth research on deflection factors and the development of straight drilling equipment and tools should be strengthened.