The invention discloses a grinding and polishing method for materials with nonuniform hardness and belongs to the field of metallographic phase sample preparation. The grinding and polishing method comprises the steps that paraffin with polyolefin is applied to a diamond disk to replace abrasive paper to conduct grinding; during grinding, automatic grinding and polishing are adopted, ultrasonic waves are adopted to wash samples every time before grinding and polishing are conducted, the load force, the grinding time and the grinding speed are controlled to guarantee that the materials with different hardnesses are ground at the same time in the grinding process and interfaces have good flatness, and the situation that dropped particles are inset into the soft material and scratch the soft material is avoided; alkaline lubricating liquid is added into diamond suspension polishing liquid so that the samples can be flat and bright. The method mainly solves the problem that the interfaces are not flat when the materials with great two-phase hardness difference are ground at the same time. The grinding and polishing efficiency is greatly improved, and waste of grinding materials is reduced.