The air curing kinetics of PCS fiber was investigated by multi-curve integral method of thermogravimetric analysis. The PCS fiber was obtained by melt spinning of PCS which was synthesized at high temperature under high pressure. The results show that the apparent active energy of curing reaction of the PCS fiber is about 60～70 kJ/mol. The relationships between the mechanism functions and the curing temperature were studied. The results show that the air curing reaction of PCS fiber is controlled by the surface reaction of random nucleation and growth mechanism (n=3). According to the reaction mechanism, the apparent active energy of curing reaction of PCS fiber is also found to be about 60～70 kJ/mol. As a consequence, the exponential coefficient, A, is about 77.64.