Abstract: The effect of annealing temperature on microstructures of cold rolled TO alloy sheet has been investigated by transmission electron microscopy, and tensile properties have been determined after annealing at different temperatures. Experimental results show that elongated cells were formed in a phase of cold rolled TCl alloy sheet, the boundaries of cells consist of high density tangled dislocations when the annealing temperature rises from 773K to 923K. the dislocation density decreases; at the same time, tangled dislocations in cell boundaries change their combination forms gradually. When the annealing temperature rises to 823K, polygonization occurs) at this time, strength decreases, but ductility does not increase. It seems that polygonization is unfavourable tor ductility. When annealing is in the temperature range of 873K to 923K, dislocation arrays and net forms apoear, then ductility increases significantly. An annealing temperature of 853±10K is recommended for cold roll ed TCl titanium alloy sheet.