A review for the fundamentals and applications of supercritical fluids (SCFs) in material processing and chemical reaction engineering was presented. The characteristics of SCFs as material processing and reaction media were discussed including the aspects of their phase behaviors and chemical reaction kinetics. Solvent-effects on phase and chemical equilibria as well as reaction rates in the vicinity of the system critical locus were elucidated. In addition, research trends and prospective applications of SCFs in reaction processes involving coal extraction, solid-catalyzed and enzymatic reactions in SCF as well as biomass hydrolysis, catalyzed oxidation and hydrothermal crystallization in supercritical water (SCW) were summarized.