In order to overcome the problems of long design cycle and high costs of grinding machine and improve the accuracy of noncircular gear,a new noncircular gear grinding method,based on 3-axis noncircular gear shaping machine has been put forward by adding form-grinding.Dividing motion data with no interference and no putting grinder up has been deduced using noncircular gear tooth generated method in the shaping process.A simple function could translate 4-axis motion data to 3-axis motion data in noncircular gear grinding process.The problem that it is difficult to grind noncircular gear hard tooth has been solved,that makes noncircular gear grinding with high accuracy became possible.