A new kind of analytics method based on laser heterodyne interferometer to achieve high lateral resolution is presented. This system needs no special platform and the size of the laser beam is several micron. The Gaussian distribution theory and the phase sum theory of laser beam are used to set up mathematics model for measuring the edge of micrograph. Modern multivariable regression techniques are applied to estimate the edge position of step. The estimation accuracy of this method is only related to measurement accuracy of measured variable. The lateral positioning accuracy of this system can reach the order of 0.1μm. On the other hand, the errors caused by the frequency mixing of the laser beam of the common-path optical system are also analyzed. The calculated curves of the errors are given and the method to reduce these phase errors is also introduced.