An Fe—Ni—P-RE multicomponent alloy plating layer, electrodeposition preparation method, and plating application. The alloy plating layer obtained via electrodeposition contains elements Fe, Ni, P and RE, with the following mass percentages Fe— 16%-65%, Ni— 25%-70%, combined Fe and Ni— 63%-91%, RE 1.6%-25%, and the balance being P. The plating solution mainly contains the following components: ferrous salt, nickel salt, NaH2PO2, RECl3, H3BO3 and Na3C6H5O7. A multicomponent alloy plating layer of different components can be obtained by adjusting the main salt and complexing agent in the plating solution and by adjusting the process Enabled is controllable adjustment to the components of the obtained plating layer while saving costs, improved characteristics such as the thermal expansion coefficient, electrical property, magnetic property, etc., and products and methods very suitable for applications in the field of micro-electronics.