Nickel Zn ferrite materials are very important soft magnetic materials for high and low frequency devices application and are good dielectric materials.While the grain size plays an important role on their magnetic and dielectric properties.In this study, XRD, TEM, isothermal and non-isothermal TG-DTA were used to study the nucleation and grain growth kinetics of Ni0.5Zn0.5Fe2O4 nano-particles synthesized via a simple sol-gel method.The results showed that the crystallization of the ferrite sample increased with increasing calcined temperatures.Evolution of the microstructure resulted in two activation energies of grain growth, the activation energies of grain growth was 1.18 kJ/mol below 850℃, and it equaled to 13.29 kJ/mol above 850℃.Where the grain growth rate was slow initially from 600 ℃ to 850℃ but increased rapidly when sintering temperature exceeded 850 ℃.