This work explores the relationship between the microstructure and mechanical properties of TC4 titanium alloy using molecular dynamics simulations. The stress-strain curves are calculated from tensile and shear tests. For the TC4 model with initial HCP structure, tensile strength along the [0001] crystal direction is larger than along the [01-10] and [2-1-10] directions. The tensile strength also increases with larger strain rate. During tensile deformation, phase transformation from HCP to BCC structure is observed, which is caused by dislocations along the close-packed direction [-1-120]. A band of amorphous structure is formed in the middle of shearing, which causes the abrupt drop in shear stress. By setting a temperature control, the heating, holding and cooling stages of heat treatment are simulated to mimic the impact of annealing, solid solution and aging. The results confirm a general trend of improved tensile and shear strength with annealing and additional solid solution and aging. With higher solid solution temperature, the amount of α phase also increases, giving rise to higher tensile and shear strength simultaneously. At the same 811 K for aging, shear strength also increases with solid solution temperature. But at the same 1227 K for the solid solution, shear strength decreases with aging temperature, in agreement with experimental results.