By the use of DTA and TBA，we observed Tgg，Tg，Tc Tm and the relative rigi-dity of p-polyphenylene sulfide．And，by the applieation of TG，DTG and DSC，the kinetics of degradation courses of PPS in air were studied．It showed that the initial degration temperature of PPS was about 400℃ (β=1℃／min)；the process of its degradation Can be divided into two stages：in the first stage

the active material of degradation is the Bnear segment of the polymer ehain in PPS strueture：but in the second stage，owing to the appearanee of condensed aromatic rings and thiocaadensed ring systems．its stability to heat resistancc had been increased，and the actiVation onergy of the degradativn was as hi．gh as 100--105 Keal/mole，the reaction order 1.7，and frequeney factor 1026 sec-1．