This paper reported a deterministic method to predict geometrical interferences between grinding wheel and workpiece on ultra-precision grinding for micro aspherical lens mould. An inclined axis grinding mode controlled by B axis is considered and investigated. For avoiding the interference between the grinding wheel and the workpiece, the relationship of the radius of the grinding wheel should be analyzed in the grinding process. In this paper, a geometrical mathematical model for avoiding interferences between grinding wheel and workpiece is built up, and three interference conditions are analyzed. The maximum diameter of the cylindrical grinding wheel is computed and obtained for grinding axisymmetric aspheric surface.