TC21 titanium alloy is a new type of titanium alloy of high strength, high toughness and damage tolerance. TC21 titanium alloy forgings with lamellar microstructure will be the right microstructure after dual annealing heat treatment to obtain high fracture toughness and low fatigue crack propagation rate, which are needed by design of excellent damage tolerance and long duration. By means of photographic and SEM techniques, the relationship between heat treatment parameters and microstructures evolvement of TC21 titanium alloy forgings has been studied. The effect-of, first annealing temperature and second annealing temperature and time on the amount and shape of lameUar structure has also been analyzed, which could lay a solid technological foundation for TC21 titanium alloy forgings to achieve high strength, high toughness and damage tolerance properties.