The invention discloses a differential pressure casting molding nonlinear pressurizing method for a copper alloy propeller hub of a large ship and relates to a pressurizing method. The method disclosed by the invention solves the problem that stable mold filling of propeller hub castings with non-uniform structural wall thicknesses is hard to guarantee as the pressurizing curve of existing differential pressure casting molding is low in control precision. The pressurizing method comprises the following steps: S1, liquid lifting process: dividing the liquid lifting process into three stages: the first stage is a liquid lifting pipe filling process, the second liquid lifting process is a cross gate filling process and the third liquid lifting process is an ingate filling process; S2, mold filling process: dividing the mold filling process into four stages; S3, pressurizing process: pressurizing the step pressure from 500 KPa to 600 KPa; S4, crystallizing and pressure maintaining: maintaining the pressurized pressure in the S3 at a pressurizing time; and S5, pressure relief. The pressurizing method provided by the invention is used for differential pressure casting molding of the copper alloy propeller hub of the large ship.