TC21 titanium alloy is a kind of titanium alloy with high strength and high toughness damage tolerance developed independently in China. In this paper, quasi-β forging, quasi-β forging +(α+β) forging and β forging process were used to forge TC21 titanium alloy. The influence of forging process on microstructure of TC21 titanium alloy and the relationship between microstructure and mechanical properties were studied by optical microscope (OM) and scanning electron microscope (SEM). The results showed that: after quasi-β forging (Tβ+15 ℃), the microstructure of TC21 titanium alloy was characterized by broken β grains and well-woven basket structure, which had good strength-plastic-toughness matching; after small deformation of (α+β) phase region after quasi-β forging, the α phases were distributed in short rod shape, and the weave degree of the basket was poor; the strength and plastic properties of the basket are similar to those of quasi-β forging, but the fracture toughness was poor; after high temperature (Tβ+25 ℃) forging, coarse and straight grain boundary α phase was formed, the strength, plasticity and toughness of the material were low.