The invention provides a method for assembling moving blades on a steam turbine rotor. All the moving blades on the steam turbine rotor are standard blades. The method for assembling all the moving blades comprises the steps of 1, arranging a wedge block used for positioning the blade root of the first blade in a slot of a rim of a steam turbine rotor wheel; 2, positioning all the moving blades in the slot one by one, and arranging a gasket between every two adjacent moving blades; 3, replacing all the gaskets with spacing pieces to make one spacing piece inserted between every two adjacent moving blades in the whole circuit of moving blades, so that assembly of the moving blades is achieved. The whole circle of moving blades can be standard blades, extra design of a final blade is not needed, an installation groove does not need to be formed in the rim of the steam turbine rotor wheel, installation of the whole circle of moving blades can be achieved through the gaskets and the spacing pieces, design cost is reduced, and the cost for manufacturing the whole circle of moving blades and the rim of the steam turbine rotor wheel is reduced.