Due to the problem of spatial interference by the high steepness, the contact measuring device can’t measure the high steepness elements surface profile error. Based on the four-axis ultra-precision machine tools and laser micro-displacement sensor, this paper introuduces a method of the measurement experiment platform. It adjusts the geometrical relationship among the machine axes by laser micro- displacement sensor. The accuracy of the measuring device system error is obtained by the high precision standard ball’s measurement. It establishes the position and the error simulation in spherical coordinate system. Applying this measuring system, it can realize the accurate measurement of the dome part’s surface profile error which includes the measuring multiple bus lines and data fitting.