Subsurface damages produced in grinding process will influence optical performance and lifetime of optical elements. The testing for subsurface damage of polished surface is research hot and difficult point now. Combination of confocal image, tomography technology, microscope optics, optical scatter and weak signal processing, a novel method based on laser confocal microscope tomography is proposed. The effects of different sizes of pinhole on measure accuracy are analyzed, and the cross section microstructure picture of the subsurface damage sample is given. The subsurface damage depth is about 45 μm with this novel method. For the same K9 glass, the subsurface damage depth is about 50~55 μm with the chemical corrosion treatment technology. The measurement results are basically consistent. Comparison with the destructive etching method shows that this novel method is good for polished surface in quantitative and non-destructive.