The invention relates to a three-dimensional ordered macroporous (3DOM) complex metal oxide catalyst for diesel soot purification and a preparation method thereof. The invention firstly provides an oxidization catalyst for combustion of soot particles discharged by a diesel vehicle, which is a simple metal oxide or complex metal oxide which selects more than one from rare-earth metal, transition metal and alkalinous metal as active components and has the 3DOM structure, wherein the average pore diameter is 50nm-1mum. The utilization of the catalyst with the 3DOM structure is beneficial to the diffusion of soot particles, improves the utilization rate of the active surface area of the catalyst, and greatly decreases the combustion temperature of the soot particles. The invention also provides a preparation method of the catalyst, comprising the step of dipping a colloidal crystal template through an organic complex agent solution that contains the active component of the catalyst, and then roasting to obtain the catalyst.