This paper describes the noncontact ultra-high accurate optical heterodyne profilometry for nanometer region. The tester is based on the heterodyne interferometry with common optical route. The surface of workpiece is illuminated by two laser beams with slightly different frequencies. One of the beams is focused as measuring optical probe to scan the surface of workpiece and the other is used as reference optical beam. The above two reflected beams are allowed to interfere. The optical phase difference of the measuring and the reference signals is in proportion to the variation of surface height. The lateral resolution is less than 2 micrometers and the vertical resolution is less than 1 nm. No extensive alignment of the sample is needed and the sample is used as reference surface also. Through the opto-electronic converter, the signal is handled by microcomputer and the microcomputer can fast accomplish measuring, calculating, displaying, and printing parameters, graphs, etc.