Abstract: According to the fact that there are some vacuoles and mosaic structures in meagre coal and anthracite in Yuxian-Xinggong coalfield of Henan province, a series of high temperature and pressure experiments were carried out on the fat coal from southern Pingdingshan coalfield. After heating at different temperature under pressure 1.5 kbar for one week, the vitrinites have been changed to some extent. The following conclusions are drawn on the basis of the experiments:vacuoles in coal form from 250-350℃, mosaic structures 350-500℃, anisotropy increases slightly when temperature is elevated. And comparing with the coal in nature, the reflectance of the heated samples with vacuoles and mosaic structures is evidently lower.