To best control the backlash of internal involute spur gears, the errors which influence the clearance in design and manufacture process are analyzed, classified and quantified. On the basis of realizing the formation mechanism and periodic change of errors, considering the feasibility of control and compensation of errors and minimum cost, this paper proposes a control and compensation method of gear backlash, including tooth thickness tolerance compensation based on equivalently modified gear, deformation compatibility design of gear, and the design formulas of minimum meshing center distance on the consideration of various errors. Then, by using the present method, two pairs of gear are taken for experiment by setting the module to 1, number of teeth to 45 and 40 respectively, precision grade to 7 and 6, respectively. The results show that the gear backlash was controlled in 3＇with present method.