In dynamical air atmosphere, the non-isothermal and isothermal thermal decomposition of FePO4·2H2O have been studied by TG, DTG, DSC and XRD techniques. The studies clearly indicate that the decomposition occurs in a single reaction step: the dehydration of FePO4·2H2O to FePO4. The model-free methods together with multivariate non-linear regression approach were employed to determine the activation energy (E), the pre-exponential factor (A) and the kinetic model function (mechanism) of the dehydration reaction. The results show that the most probable kinetic model of dehydration for FePO4·2H2O is well described by the nth-order reaction (Fn), corresponding to the differential function f(α)=(1− α) n . For non-isothermal reaction, the values of n, E and ln(A/s−1) are 0.63, 81.10kJmol−1 and 16.79, respectively. For isothermal reaction, the values of n, E and ln(A/s−1) are 0.25, 81.47kJmol−1 and 16.70, respectively.