In this paper, the dislocations in heavily doped P-type 6H-SiC crystals grown by liquid phase method have been studied in detail by melt KOH etching method. The effects of etching time and temperature on the surface etching of the heavily doped P-type 6H-SiC wafers grown by liquid phase method were investigated. The increase of etching temperature or etching time enlarge the etching pit size on the wafer surface, and the over etching happen at over temperature and long etching time. The optimal parameters for etching heavily doped P-type 6H-SiC wafers were determined according to the morphology and distribution of etching pits under different etching conditions. The reaction activation energy of the heavily doped P-type 6H-SiC crystal is calculated to be 10.59 kcal/mol through the etching rate variation relationship of the wafers at different temperatures and Arrhenius formula. Finally, the detailed characterizations on the morphologies, sizes and internal structures of threading screw dislocation (TSD) and threading edge dislocation (TED) in the wafers indicate that the inclination angle of etching pits in P-type 6H-SiC crystals is independent of the etching time.