The invention discloses an oil pump adopting a three-gear structure. The oil pump consists of a pump body (1), two driven gears (2), a mounting bolt (3), a pump cover (4), a positioning bolt (5), a driving gear (6) and a pressure-limiting valve (7). According to the oil pump, a three-gear structure is designed to pump oil, three gears are tightly meshed, the flow quantity of the pumped oil is large, the transmission is stable, and the hydraulic pulsation is small.