Abstract: In order to improve the thermal oxidative aging resistance of Salix psammophila (SPP)/ polylactic acid (PLA) composites, zinc oxide (ZnO) was used as an inorganic functional additive, and ZnO-SPP/PLA composites were prepared by two-step addition process and compression molding process. The composite mode and mechanism of ZnO and SPP and the effect of ZnO on the mechanical properties, thermal stability and thermal-oxidative aging resistance of composites were emphatically studied. The results show that ZnO and SPP can be grafted by KH550. When 3%ZnO was added, the flexural strength, elastic modulus and impact strength of the composites reached the optimal values of 26 MPa, 3241 MPa and 3.54 kJ/m², which were increased by 28%, 33% and 39% respectively compared with the blank samples. The thermal stability of the composites was significantly improved, and the initial degradation temperature, the maximum weight loss rate temperature T_max and the residual carbon content were increased by 121℃, 196℃ and 20.7% respectively compared with the blank samples. After thermal oxidation aging at 80℃ for 128 h, the retention rates of static bending strength, elastic modulus and impact strength of the composites were 84%, 80% and 87%, respectively, which were 22%, 12% and 25% higher than those of the blank samples. The contact angle decreased from 123.8 to 113, which was 35 and 40.4 higher than that of the blank sample. The mass loss rate is only 1.58%; Compared with the blank sample, the initial degradation temperature, T_max and carbon residue of the composite increased by 41℃, 27℃ and 12.9%, respectively, and the thermal-oxidative aging resistance of the composite was significantly improved.