The invention discloses an engine oil pump with a pneumatic motor driving pre-lubricating device. The engine oil pump comprises an oil pump shell, a motor end outer shell cover is fixedly arranged on the left side wall of the oil pump shell through screws, an oil pump end outer shell cover is fixedly arranged on the right side wall of the oil pump shell through screws, a pneumatic motor is arranged at the left side end of an inner cavity of the oil pump shell, wherein the pneumatic motor comprises a pneumatic motor rotor, a pneumatic motor overrun clutch roller and pneumatic sliding sheets, a transmission shaft is rotationally connected to the middle of the inner cavity of the oil pump shell, the pneumatic motor overrun clutch roller is fixedly arranged on the outer side wall of the left side end of the transmission shaft, the pneumatic motor rotor is fixedly arranged on the outer side wall of the pneumatic motor overrun clutch roller, the pneumatic sliding sheets are uniformly inserted into the inner cavity of the pneumatic motor rotor, and an air outlet is formed in the left side of the top of the oil pump shell. According to the engine oil pump, by controlling the operation of the oil pump, the comprehensive effects that the pre-lubricating effect is achieved, the pre-lubricating parts are comprehensive, and the effect is good are achieved.