The invention relates to a ground conveying screw pump or a downhole oil production screw pump, in particular to a crank type crankshaft drive single screw pump, which is designed against the technical problems that a connecting structure between a rotor and a drive shaft in the similar screw pump is poor, thereby causing high cost and easy abrasion. The design key points are as follows: the drive shaft and the rotor are in crankshaft type connection through a balancing assembly, the balancing assembly consists of connecting bodies and a balancing part, and the gravity centers of the connecting bodies are eccentrically arranged relative to the rotation central line of the drive shaft and the rotor. The gravity center of the balancing assembly is positioned on the rotation central line of the drive shaft and the rotor by setting the balancing part. One end of the rotor is connected with the balancing assembly, the other end is connected with a balancing block, and the gravity center of a whole constituted by the balancing block and the rotor is positioned on the rotation central line of the drive shaft and the rotor. The crank type crankshaft drive single screw pump can not only reduce the abrasion of a connecting part and the vibration of a drive component, but also prolong the service life of the screw pump and improve the working stability.