Wire arc additive manufacturing（WAAM）technology has the characteristics of high production efficiency and low cost,but in order to ensure the comprehensive performance of the parts produced by WAAM,post heat treatment is often required. In this study,TC4 sample is fabricated by WAAM,and through the optical microscope,scanning electron microscope,X-ray diffraction,tensile testing machine and the hardness tester,the effect of cooling rates（water cooling（WC）,air cooling（AC） and furnace cooling（FC） at950 ℃ for 2 h） on microstructure and mechanical properties of TC4 is studied. The results show that the microstructures of the TC4 samples under WC,AC and FC modes are composed of primary α phase and β phase,and more β phase is obtained under the WC mode. The microstructure of the TC4 sample shows a tendency of coarsening gradually from the lower part to the upper part. As the cooling rate decreases,the primary αphase gradually coarsens,and the tensile strength of the TC4 sample reduces,and the plasticity increases. The mechanical properties of TC4 sample with 950 ℃ ×2 h/AC exceeds the requirements of the national standard of casting, and the appearance of fracture of tensile samples shows plastic fracture.