The surface topography measurement technique and system based on structured light illumination is studied around the demand of high precision measurement of scattering surface and complex microstructure surface topography. A structured light illumination optical system with good structured light contrast and uniformity based on Kohler illumination combined with digital micromirror device (DMD) modulation is designed. A virtual slit SlitMask structured illumination confocal sectioning algorithm using Gaussian curve interpolation is proposed, and the surface topography reconstruction through iterative Gaussian fitting is achieved. A structured illumination surface topography measurement system is established and well verified by experimental tests. The accuracy and repeatability of the system are tested with a single groove specimen. The results show that the relative measurement error is 1.87%, and the standard deviation of the repeated measurement results is 0.0014 μm. Furthermore, tests on actual industrial samples such as glass multiple carved lines and turned surface prove that the system can not only be used for the measurement of reflective surfaces, but also has good measurement capability for scattered surfaces.