The isothermal oxidation behaviors at 800-1000°C for 20h in air of bulk Ti2AlN and Ti2AlN/TiN were investigated by TG, XRD and SEM coupled with EDS. The oxidation behaviors generally follow the parabolic law. The activation energies of Ti2AlN and Ti2AlN/TiN composite are 614.93 KJ∙mol-1 and 541.35 KJ∙mol-1 respectively. The antioxidation property of Ti2AlN/TiN composite is better than Ti2AlN. Oxidation process of single-phase Ti2AlN is composed by the outward diffusion of Al3+ and Ti4+, and inward diffusion of oxygen. Oxidation process of Ti2AlN/TiN composite consists of two parts: firstly, the oxidation of TiN, the oxidation temperature is 500 °C; the second step is the oxidation of Ti2AlN, carried out mainly in the 800-1000 °C.