Abstract: During directional drilling using screw drill,difficult adjustment of tool face as well as back pressure in slide drilling are often encountered due to the high drag force of the wellbore.To address these problems,a slide drilling control system based on the top drive’s programmable logic controller(PLC) integrated with sensors was researched and developed by utilizing accurate positioning and rotation from top drive,The variation of the friction of drill string before and after sliding as well as the method of reducing wellbore drag by controlling drill string rotary torque were researched and analyzed.Through the real-time data acquisition of 5 sensors,the experiences and reasoning methods of directional driller are transformed to a set of control program,thus a human-computer interaction interface with PLC as the core is built.The PLC calculates the rotary angle required at the tool face and then accurately adjusts the tool face angle to the designed angle.The hook weight and differential pressure are used to determine if back pressure.After the rotary torque value without making any changes of the tool face angle is calculated by PLC,the top drive rotates the drill string clockwise or counterclockwise according to calculated torque value to reduce the wellbore drag until the differential pressure is greater than zero,thus sliding back pressure could be solved.Application result shows that the new method can significantly reduce wellbore drag force and improve the ROP,and is currently the most effective method in solving screw drill slide drilling.