With thermogravimetric analyzer, the pyrolysis characteristics of three kinds of lignin from agricultural wastes were studied under three heating rates (10, 20, and 40 K/min). The increase of heating rate could advance the final pyrolysis degree and the pyrolysis reaction rate. In the main pyrolysis region, the lignin samples of corn cob (CC) and peanut shell (PS) showed two peaks of reaction rate curves, yet three peaks for the pine cone (PC) lignin. With the model-free Starink methods, it was found in the previous sections of all the lignin samples, the E values changed widely, and yet in the last sections, the E values were fairly stable. With the model-fitting methods, the kinetic parameters of CC and PS showed a good consistency: both of the lignin pyrolysis processes fitted F1 model for Coats-Redfern method and F1.5 model for Horowitz-Metzger method, and the E values of the two lignin pyrolysis were fairly close; yet, the parameters of the pyrolysis process of the PC lignin obtained were different from these of the other two lignin samples: the model was F2 model for Coats-Redfern method and F3 model for Horowitz-Metzger method. Finally, the E values of the different methods were compared: Starink method > Horowitz-Metzger method > Coats-Redfern method.