The invention discloses a connecting device for transmitting power. The connecting device comprises a motor assembly, a hydraulic transmission assembly, and a connecting assembly arranged between themotor assembly and the hydraulic transmission assembly. The connecting assembly comprises a power transmission shaft, a power connection disc and a torque converter which are sequentially arranged. Alarge end plate of the power transmission shaft is connected with the power output end of the motor assembly through an output flange, and the tip of the small end of the power transmission shaft is fixedly connected with the power connection disc through a connecting piece. The connecting assembly arranged between the motor assembly and the hydraulic transmission assembly is compact in structureand reasonable in layout, all parts of the connecting assembly are easy to manufacture and low in machining cost, mounting and dismounting are convenient, the reliability requirements of radial and axial connection when the motor assembly and the hydraulic transmission assembly realize power transmitting through the connecting assembly are met, and the power transmitting effect is good.