The invention provides an oil-well pump with double load reduction and gas locking prevention functions and is applicable to the field of oil production engineering. The oil-well pump is provided with a lifting sub; a small pump cylinder and a large pump cylinder, which are connected with each other are arranged at one end of the lifting sub; a small piston and a large piston, which are capable of sliding in the axial direction are embedded into the inner cavities of the small pump cylinder and the large pump cylinder respectively; and by arranging the two pistons in a combined manner, that the displacement of the oil-well pump is the displacement of the large piston is ensured, and meanwhile, the load of the oil-well pump is obviously reduced. The interior of the other end of the lifting sub is fixedly connected with an upstream movable valve cover and a valve seat; a pumping rod penetrates through the lifting sub and the two pistons; the end part of the pumping rod is connected with a downstream movable valve capable of propping against and sealing the large piston; and an upstream movable valve capable of being matched with the valve seat to be opened and closed is movably connected with the pumping rod in a sleeving manner. During switching of the upper stroke and the lower stroke of the oil-well pump, the pressure of the oil in an oil pipe can act on the upstream movable valve, so that the impact load to the pumping rod is reduced. In addition, the opening and closing of the downstream movable valve can be controlled through the pumping rod, so that the function of gas locking prevention is realized.