Coal char particles were deposited on the molten slag surface and continued to react with the gas near the gasifier wall slag surface in an entrained flow gasifier, which significantly affected the total carbon conversion and slag flow properties. The current research work is to investigate the fragmentation and gasification characteristics of coal char particles, which were captured on the molten slag surface. A high-temperature stage microscope was used to study and analyze the particle evolution and char gasification process on the molten slag surface with the effects of different coal ranks. Results indicated that char particles first shrank and then broke into several fragments during the gasification on the molten slag surface. Char particles with fragmentation behaviors on the molten slag surface had higher reaction rates and carbon conversions than the particles in the shrinking period. The initial fragmentation time of a char particle showed an increasing linear relationship with the initial particle size and coal rank. The number of fragments for a char particle displayed a relationship of Gaussian function distribution with the reaction time. A fragmentation intensity factor defined in this study increased with the contents of moisture and volatiles in the raw samples, which means that char particles with a low coal rank could easily break into fragments on the molten slag surface. The ash content in the raw sample also affected fragmentation and gasification behaviors of char particles when reacted with CO2 on the slag surface.