Non-isothermal Pyrolysis kinetics phenol-formaldehyde（PF) resin is investigated using thermogravimetry（TG). The TG experiments at controlled heating rates were used for obtaining the kinetic parameters of the reactive system. The research indicates that the pyrolysis process consists of four consecutive distinct stages. The anterior two stages are named as one-dimensional diffusion and three-dimensional reaction regions，while the third stage is characterized as a random nucleation and its subsequent growth，and the latest one can be defined as a chemical reaction region. According to the calculation results of the apparent activation energy Ea，the changes of entropy △S≠，enthalpy △H≠and Gibbs free energy △G≠，the anterior three stages are non-spontaneous processes. While the fourth stage proceeds spontaneously.