In this work, chili straw (CS) was pretreated by microwave at 250 W, 406 W, 567 W, and 700 W. The pyrolysis characteristics, kinetics, thermodynamic parameters, and solid reaction mechanism were investigated. The maximum weight loss rate increases from - 24.72%/°C at P0 to - 28.01%/°C at P700 after microwave pretreatment, and the residual mass decreases from 31.81 at P0 to 26.71% at P700. In addition, microwave pretreatment leads to a decrease in activation energy, ∆H, and ∆G at the end of the pyrolysis (α > 0.7). The solid reaction mechanism of CS pyrolysis is revealed by the Z-master plots method, with un-pretreated CS conforming to P2, D4, F3/2, and F3, respectively. Microwave pretreatment changes the solid reaction mechanism mainly in the third stage, when α = 0.8, the mechanism function changes from f(α) = (1 - α)3 at P0 to f(α) = (1 - α) at P700, and the number of reaction order is reduced, which is profitable for CS pyrolysis.