A submerged oil pump unit provided with a downhole drive conversion device comprises a control cabinet, a reciprocating oil pump, an asynchronous starting and permanent magnet synchronous type rotary submersible motor and a reciprocating load balanced type downhole drive conversion device, wherein the control cabinet realizes an automatic phase change function by means of a set load value according to the set frequency; the rotary submersible motor is located in a downhole casing and provided with a protector; the downhole drive conversion device is arranged between the submersible motor and the oil pump. The submerged oil pump doesn't need long-rod transmission and can adapt to well conditions of multiple turning points, high inclination, high lift and the like which are not adapted during long-rod transmission. Compared with a linear type submersible motor, the rotary submersible motor has high output power and high efficiency; compared with a conventional rotary submersible motor or a permanent magnet motor, the rotary submersible motor has good starting performance and high force and energy indexes; compression springs are arranged at two ends of the downhole drive conversion device, and the operation reliability can be improved; by means of oil storage rubber bags arranged at two ends, the reliability of the sealing performance of an inner cavity of the drive conversion device can be guaranteed. The device can meet demands for different lift and displacement of most oil wells and can reliably operate for a long time.