The invention provides a material mixing method of graphite negative electrode slurry. The graphite negative electrode slurry comprises a first graphite material, a second graphite material and a third graphite material, wherein the average grain diameter of the first graphite material is d1, the average grain diameter of the second graphite material is d2, and the average grain diameter of the third graphite material is d3, wherein d1 is smaller than d2 which is smaller than d3, and d2 is equal to k*(d1+d3); k is equal to a*(c1+c3)/(c2+0.5), wherein a is an equilibrium constant, and a is greater than or equal to 1.1 and less than or equal to 1.3; c1, c2 and c3 represent percentages of the first graphite material, the second graphite material and the third graphite material; and c1+ c2 +c3is equal to 1, and c1+c2 is less than or equal to c3. The material mixing method comprises the following steps of carrying out mixing on the first graphite material, the second graphite material andthe third graphite material to obtain three slurry materials respectively, and then enabling the three slurry materials to be mixed according to a specific sequence to obtain the graphite negative electrode slurry with high dispersion degree. The graphite negative electrode slurry disclosed by the invention is high in graphite dispersion degree, free of agglomeration, free of sedimentation, high in storage stability, high in energy density and high in rate performance.