The invention belongs to the field of mechanical manufacturing, and particularly relates to a method for designing a marine crankshaft shrinkage range, which is applicable to the designing and manufacturing processes of marine crankshafts. The method comprises the following steps: determining the minimum value of the crankshaft shrinkage range in an analytic method and according to force-bearing requirements of the integral structure after crankshaft shrinkage; determining the maximum value of the crankshaft shrinkage range in the analytic method and according to requirements that the material is yielded after crankshaft shrinkage; and adopting a finite element for simulation, selecting an appropriate value between the maximum value and the minimum value, so that the part bearing the maximal stress in the overall system can not be yielded in the shrinkage sampling range, and serving the value as a value of optimum shrinkage sampling. The large marine crank shaft obtained after shrinkage fit in the invention can ensures that shrinkage fit hole spalling caused by interfacial stress can be reduced remarkably, the structure after shrinkage fit can bear the rated torsion torque, so that slippage is generated. Therefore, risks for manufacturing are reduced, the finished product ratio is improved, and the production cycle of crank shaft products is reduced.