Silicon tetraboride (SiB4) is one of the indispensable functional filler of current high-emissivity thermal protection coating, which protects hypersonic aircrafts with speed of Mach number 5 and above from extremely high temperature environment. With the increase of reusable launch vehicles’ (RLV) speed, nowadays the demand of coating service safety and reliability has also been put forward for higher requirements. It is very of significance to understand the oxidation model and kinetic of SiB4, hence, so that can make further improvements of coating properties. The oxidation kinetics of SiB4 powders with particle size of 40 μm in air flow at temperature up to 1300 ℃ was investigated using non-isothermal analysis at 5 ℃/min, 10 ℃/min and 20 ℃/min, and the Flynn-Wall-Ozawa (FWO) method also been utilized to calculate the activation energy Ea, the preexponential factor A and the oxidation kinetic model function. The results show that starting temperature of oxidation reaction of SiB4 powder was about 650 ℃, and TG curves had three distinguishable stages in the temperature ranges of < 650℃, 650-1000℃ and 1000-1300 ℃ accompanying a trend of mass constant → mass gaining → mass constant. There were two reasons, which were the protecting of SiO2-B2O3 glass and the competitive effect between volatilization of B2O3 and mass gaining for oxidation of SiB4, respectively, for the mass constant of SiB4 samples at high temperature stage. And there was an obviously connection between the heating rates and SiB4 oxidation that the faster temperature rises, the more obvious the exothermic effect. The activation energy of 40 μm silicon tetraboride was 239.14 kJ/mol and the preexponential factor was 2.1901×104 K/s. The conversion function of oxidation reaction of SiB4 was G(α)=ln[-ln(1-α)]^1.7574.