The effects of aging after solution-treatment and aging after cold-working on the microstructure and mechanical properties of a commercial beta titanium alloy Ti-13V-11Cr-3Al were investigated. In the aging after solution-treatment, preferential alpha precipitation on beta grain boundaries is remarkable in the aged microstructure and, with increase in aging time, strength increases, however, ductility decreases greatly due to the development of grain boundary cracking. The grain boundary cracking is caused by the preferential precipitation of alpha phase on the beta grain boundaries. In the aging after cold-working, cold-working remarkably promotes aging response and greatly improves strength-ductility balance after aging through suppressing preferential precipitation of alpha phase on grain boundaries and getting more uniform and finer aged microstructure. In this heat-treatment, higher reduction in cold-working and lower temperatures in aging are preferable to the improvement of mechanical properties.