The invention discloses a double-action oil well pump used for rodless oil extraction. The double-action oil well pump comprises an upper coupling, a long pump cylinder, a long plunger, a lower pump coupling, a short pump cylinder and a lower coupling. The double-action oil well pump is characterized in that an upper pump oil outlet valve is arranged at the upper end of the long pump cylinder; a liquid inlet is formed in a side wall of the long pump cylinder; a movable joint seat is arranged at the lower end of a short plunger; an end cap is arranged at the upper end of the short plunger; the lower end of a movable joint penetrates through the movable joint seat at the lower end of the short plunger and is connected and fixed with the upper end of the long plunger; a flow converter is arranged at the lower end of the upper coupling; a middle flow channel and a side flow channel are formed in the flow converter; a lower end opening of the side flow channel is fixedly connected with an outlet of the upper pump oil outlet valve; an upper end opening of the side flow channel is communicated with an inner cavity of the upper coupling; a lower end opening of the middle flow channel is communicated with an oil outlet of the lower pump coupling through a high-pressure oil pipe; an upper end opening of the middle flow channel is connected and fixed with the lower pump oil outlet valve; and the oil outlet of the lower pump coupling is communicated with the bottom of a lower pump cavity. According to the double-action oil well pump, twice liquid feeding and twice liquid discharging are finished by one stroke, so that the liquid production capacity of a single well is increased.