The invention relates to a sand blasting pretreatment method for preparing a hard alloy matrix diamond coating. The method is specific to hard alloy matrixes. Firstly, the surface of a hard alloy matrix is subjected to erosion coarsening through the sand blasting technology, then cobalt removal is conducted on the matrix through acid treatment, and the surface appearance which is suitable for growth of a diamond film and is evenly coarsened is prepared. Compared with a conventional acid-base two-step pretreatment method, the sand blasting pretreatment method can effectively control the surface roughness of the hard alloy matrix, and the nucleation density of the initial deposition stage of a diamond coating is greatly improved; and in addition, no porous layer is generated after pretreatment is completed, and thus the adhesive force between the diamond coating and the matrix is effectively improved. The pretreatment method is not limited by matrix shapes and is suitable for preparation of the diamond coating of the hard alloy matrix in complex shapes, operation is easy, application is convenient, the production efficiency is high, pollution is avoided, the industrial prospects are bright, and accordingly the sand blasting pretreatment method has remarkable economic benefits.