A crankshaft clamping unloading device relates to the improvement of a clamping device of a part of a large-scale grinder to be machined and is mainly used for a clamping device for grinding heavy parts and parts which need centering of center holes. The invention aims at providing a crankshaft clamping unloading device with simple structure and convenient operation. The crankshaft clamping unloading device comprises a part chuck, wherein, the structural key point is that: the outer edge of the part chuck is provided with a stud bolt which is connected with a main shaft chuck; a spring is arranged between a gland of the stud bolt and the part chuck; and the part chuck is provided with screws for fixing the parts.