The pyrolysis characteristics of stalk, bark, xylem, and pith of cotton were studied by means of STA449c thermo gravimetric apparatus. The process was carried out with heating rates of 5, 10, 20, 30℃/min and final temperature of 600℃ under the atmosphere of nitrogen. TG-DTG curves for these four samples showed that their properties agreed with similar laws of pyrolysis. The pyrolysis of the samples was divided into 4 stages: extraction of water, pre-heating, main pyrolysis and charring. As the ash content of cotton bark was the highest among the different components of cotton, it produced more residues after the pyrolysis process. Xylem and pith of cotton, which were more volatile components, had a larger rate of weight loss. The optimized mechanism and the corresponding function G(α), f(α) were derived from the regression of Stava and Achar. The results showed that when α was 10%－80%, the activation energy of the four substances were relatively stable. However, the activation energies for cotton bark were found relatively higher than the others. The kinetic mechanism of the four substances could be best described by Avrami-Erofeev equations, which belonged to the random nucleation and subsequent growth mechanism. The reaction orders of samples were different according to the experimental results. The study provides a good reference for cotton stalk waste recycling and biomass pyrolysis device design, as well as process parameters optimization.