Test method for measuring austenite and martensite microscopic grain size of the steel is commonly done. Determination of average crystal density for the specimen is defined by JIS (Japanese Industrial Standards) in Japan. In general, this kind of determination is carried out by engineers. The results may depend on their skill, so automated tool to determine the grain size is needed. In this paper we try to apply homology method to analyze the structures. As the first trial, we apply this method to the figures on JIS. The result of homology is compared with the grain size defined in JIS. We can make sure the correlation between grain size and the homology value.
