Oil well pump of horizontal heavy oil well

The utility model discloses an oil well pump of a horizontal heavy oil well, which comprises an upper pump cylinder (1), a lower pump cylinder (2), a pump cylinder upper joint (3), a pump cylinder lower joint (4), a plunger piston pull rod (7), an upper floating plunger piston (8), a lower sealing plunger piston (9) and a middle plunger piston pull rod (29), wherein an upper righting joint (11) is arranged at the upper end of the plunger piston pull rod (7), the lower end of the plunger piston pull rod (7) is connected with the middle plunger piston pull rod (29) through a mechanical forced valve ball (28) and a middle righting joint (12), the middle plunger piston pull rod (29) is connected with a lower righting joint (13), a connecting pipe (14) in a cavity of a nipple (15) is connected with the lower righting joint (13) through an oil inlet valve (20), the connecting pipe (14) is connected with the lower sealing plunger piston (9), and a gap bridge upper joint (5) and a gap bridge lower joint (6) are in th