The catalytic functionality and structural properties of three kinds of unsupported molybdenum sulfide catalysts were investigated by model test reactions and BET, TEM, XPS and XRD analyses. The results indicated that highly bent multilayered MoS2 structures were more catalytically active, while a well crystallized MoS2 structure was more favorable for direct S-extrusion during the reactions of dibenzothiophene. It was proposed that the curvature of MoS2 basal planes was catalytically active, though they were less active for hydrodesulfurization than the edge planes.