The utility model relates to a rhombus rotor motor. The utility model has the technical proposal that the rhombus rotor motor comprises a shell body, a rotor center and end closures; wherein, both sides of the shell body are respectively provided with the end closures. The rotor center comprises four sliding blades, two supporting shafts, four radial gland strips, four axial gland strips, a power wheel and two slide blocks, every two sliding blades in the four sliding blades are connected with each other to form a rhombus, and along with the shape change of the rotor center. The support shafts on the two sliding blades are mutually affected with two supporting shaft holes on the power wheel respectively, thereby transferring the motive power to a main shaft. During the rotation and shape change process of the rotor center, the power wheel is positioned at the geometric centre of the rotor center all the time; in addition, the power wheel revolves synchronously along with the connecting line between wring centers of sealed wrings at the diagonal positions of the rotor center. The utility model has the advantages of less moving parts than that of a rotary engine, eliminating the reciprocating movement thoroughly in theory, the vibrationless engine without regard to manufacturing errors, and higher thermal efficiency.