The invention relates to a laser additive manufacturing method for a homogeneous functionally graded material and structure. The method includes the following steps that different functions are mapped into different temperatures which serve as boundary conditions to be exerted on different parts of a three-dimensional model; a three-dimensional finite element method is used for calculating a heat conduction equation of the model, inner temperature graded distribution, namely the temperature field of a model, is obtained, that is a temperature field of the model is obtained; an isothermal surface of the model is extracted, and a curved surface set with different temperature marks is obtained; slicing is conducted on the curved surface set, the intersection outline of each layer and the isothermal surface is obtained, in other words, plane isothermal lines are obtained; slices of each layer are processed, and a scanning route with laser parameters of the single layer in graded variation is obtained; the steps are repeatedly conducted until slicing is completed and a laser scanning route of the model is obtained; the generated laser scanning route is input into a laser 3D printing machine to control the additive manufacturing process, and the homogeneous functionally graded structure is obtained. According to the additive manufacturing method, the fact that the homogeneous functionally graded material and the homogeneous functionally graded structure can be manufactured in an additive mode is achieved, and the fact cannot be achieved through a current laser additive manufacturing method.