A new non-destructive method was developed to identify the grinding mode of silicon wafers, which is based on the information of subsurface cracks extracted from the surface topography of the ground silicon wafers measured with a 3D surface profiler. We examined extensive measurement data of the surface topography of silicon wafers processed by single grain grinding or real grinding operation, and our results show that the information about median cracks could be captured if the lateral sampling interval of the 3D surface profiler is small enough, even if the grain depth of cut is below 20nm. If the maximum valley of the measured surface topography is approximately equal to the grain depth of cut, surface formation will be under ductile mode, whereas, if the maximum valley is several times larger than the grain depth of cut, surface formation will be under brittle mode. According to this criterion, silicon wafers ground by ductile mode or brittle mode could be identified rapidly and conveniently. Experimental validation shows that this method is accurate.