This paper brings a new method of adaptive control with constant pressure on large-scale surface grinding machine. The existing problem of uneven in the process of abrasive belt grinding on titanium alloy composite plates is solved effectively. And the grinding head and the belt follow the plate surface ups and downs effectively through contacting the workpiece with the constant pressure. Not only did ensure the grinding depth and the size of the titanium alloy plates, but also improved the surface processing quality. After experiment, the satisfactory control effect was obtained. The research results have some practical value on adaptive control theory and industrial practice.