DSC non isothermal multiple scan curves were applied to investigate the pyrolysis kinetics of chitosan and chitin.The apparent activation energy(E) and frequency factor(lnA) for thermal decomposition were(157.81 ± 1.23) 、(171.67 ± 3.16) kJ/mol and(26.49 ± 0.26) 、(24.20 ± 0.62) min-1,respectively.And the most probable mechanism functions were obtained by Achar’s differential method.The functions of chitosan and chitin were f(α) =2(1-α) 3/2 and f(α) =3/2(1-α) 2/3[1-(1-α) 1/3]-1,which was considered as 2/3 order chemical reaction and 3D diffusion and ball symmetry mechanism.