A method for carrying out diffusion treatment on a coating of engineering parts resistant to marine climate, comprising: a first step: pre-treating the parts; a second step: preheating the parts in a protective atmosphere furnace; a third step: immersing the preheated parts in a plating solution in a way that the parts are rotated in the submerging process; and a fourth step: undergoing diffusion treatment, particularly, putting the immersion-plated parts into a vacuum furnace, holding at 800 - 950 °C for 1 - 3 hours, then, reducing the temperature gradually and taking out the parts, and forming a diffusion layer on a substrate through the diffusion of atoms at the interface to achieve the metallurgical combination between the coating and the substrate, characterized in that in the third step the preheated parts are put in the plating solution for 1 - 5 minutes, said plating solution mainly contains Zn, Al, Si, RE, microalloy elements and a nanometer oxide particle reinforcing agent, said nanometer oxide particle reinforcing agent is selected from one or two of TiO 2 and CeO 2, said microalloy elements are selected from one or more than one of Mg, Ti and Ni, and the mass percentages of the components of the plating solution are as follows: Zn: 35 - 58 %, Si: 0.3 - 4.0 %, RE: 0.02 - 1.0 %, the total content of the nanometer oxide particle reinforcing agent: 0.01 - 1.0 %, the total content of the microalloy elements: 0.01 - 6.0 %, and Al: the balance, wherein the average particle size of said nanometer oxide particle reinforcing agent is 15-60 nm, and wherein the mass percentages of the specific adding amounts of the components of said microalloy elements are as follows: Mg: 0.1 - 5.0 %, Ti: 0.01 - 0.5 %, and Ni: 0.1 - 3.0 %. a first step: pre-treating the parts; a second step: preheating the parts in a protective atmosphere furnace; a third step: immersing the preheated parts in a plating solution in a way that the parts are rotated in the submerging process; and a fourth step: undergoing diffusion treatment, particularly, putting the immersion-plated parts into a vacuum furnace, holding at 800 - 950 °C for 1 - 3 hours, then, reducing the temperature gradually and taking out the parts, and forming a diffusion layer on a substrate through the diffusion of atoms at the interface to achieve the metallurgical combination between the coating and the substrate, characterized in that in the third step the preheated parts are put in the plating solution for 1 - 5 minutes, said plating solution mainly contains Zn, Al, Si, RE, microalloy elements and a nanometer oxide particle reinforcing agent, said nanometer oxide particle reinforcing agent is selected from one or two of TiO 2 and CeO 2, said microalloy elements are selected from one or more than one of Mg, Ti and Ni, and the mass percentages of the components of the plating solution are as follows: Zn: 35 - 58 %, Si: 0.3 - 4.0 %, RE: 0.02 - 1.0 %, the total content of the nanometer oxide particle reinforcing agent: 0.01 - 1.0 %, the total content of the microalloy elements: 0.01 - 6.0 %, and Al: the balance, wherein the average particle size of said nanometer oxide particle reinforcing agent is 15-60 nm, and wherein the mass percentages of the specific adding amounts of the components of said microalloy elements are as follows: Mg: 0.1 - 5.0 %, Ti: 0.01 - 0.5 %, and Ni: 0.1 - 3.0 %. characterized in that in the third step the preheated parts are put in the plating solution for 1 - 5 minutes, said plating solution mainly contains Zn, Al, Si, RE, microalloy elements and a nanometer oxide particle reinforcing agent, said nanometer oxide particle reinforcing agent is selected from one or two of TiO 2 and CeO 2, said microalloy elements are selected from one or more than one of Mg, Ti and Ni, and the mass percentages of the components of the plating solution are as follows: Zn: 35 - 58 %, Si: 0.3 - 4.0 %, RE: 0.02 - 1.0 %, the total content of the nanometer oxide particle reinforcing agent: 0.01 - 1.0 %, the total content of the microalloy elements: 0.01 - 6.0 %, and Al: the balance, wherein the average particle size of said nanometer oxide particle reinforcing agent is 15-60 nm, and wherein the mass percentages of the specific adding amounts of the components of said microalloy elements are as follows: Mg: 0.1 - 5.0 %, Ti: 0.01 - 0.5 %, and Ni: 0.1 - 3.0 %.