Abstract: The oil pump for a vehicle may include a housing forming an outer wall of the oil pump, an outer ring to control a pumping volume of an oil, a first chamber for storing a pumped oil and connected to an engine to supply the oil to the engine, a second chamber selectively communicated to the first chamber to store the pumped oil, a rotor moving along a radial direction to pump the oil and rotating at the same time, an elastic member for controlling an operation pressure of the oil to maintain a working moment of the outer ring, and a solenoid valve for selectively communicating the first chamber with the second chamber.