The invention discloses a method for producing a nonhuman mammal transgenic animal. The method comprises the following steps of: (1) constructing an expression plasmid vector containing a target gene GFP (Green Fluorescent Protein); (2) preparing a cationic liposome complex containing the target gene GFP; (3) directly transfecting the cationic liposome complex containing the target gene GFP into an early embryo or fertilized egg of a nonhuman mammal animal by using the cationic liposome complex containing the target gene GFP to obtain a transgenic embryo containing the target gene GFP; and (4) transplanting the transgenic embryo containing the target gene GFP into a receptor animal. In a technology of the invention, a cationic liposome and the expression plasmid vector containing the target gene GFP are co-incubated, and are introduced into the early embryo or fertilized egg of an animal. The method is easy, convenient and efficient; and moreover, intermediate products such as plasmids and the like are stable in an operating process, and a transgenic animal with stable trait can be obtained.