Abstract: An in situ quasidynamic observing method for the morphology evolution of the wear surface by a scanning electron microscope (SEM) was proposed. This method was capable of positioning and observing discontinuously the wear surface and had no the limitation of the stationary and in-situ dynamic observing methods. By constructing the coordinate system on the specimen surface and positioning according to the coordinate and morphological characteristics,the tested position could be determined conveniently and precisely. Making the friction direction vertical to the line scanning direction of the electron beam and the specimen surface slant properly to the secondary electron detector (SED), the effect of the observing and photographing could be improved. The morphology evolution of the carbides (Fe,Cr) 7C 3 in high chromium cast iron sliding against fixed SiC particles was observed with the method.