Northwest Jurassic roof cracks water is the main type of water disaster of coal mine in China, the roof water seriously influences the normal production and causes hidden dangers for safety. The control scheme of roof water drainage by long directional borehole was put forward by directional drilling technology with MWD to solve this problem, and the drilling technology and drilling equipments have been matched. The test has implemented smoothly in 3121 working face of Hongliu mine, which shows the average water discharging amount of the long directional borehole is 269 times of that of the conventional borehole in adjacent working face, the discharging amount is 415 times of that of the conventional borehole in the same discharging cycle. Drainage was simultaneously carried out in 2 roof aquifers, the safe mining requirements are achieved with drainage effect in the advance long distance regions and 78% construction period being saved. The practice proves that directional drilling with MWD has broad application prospect in the roof water control.