A study on CaSO4:Dy TLDs was undertaken to confirm the validity of the annealing treatment (400°C,1h) for its re-use. The temperature range of the study was from 230°C to 700°C. The effect of thermal treatments on the TL sensitivity and glow curve structure showed that the lattice of CaSO4:Dy is sensitive to thermal treatment in the temperature range from 350°C to 425°C. It is also seen that both TL sensitivity and peak height ratio (dosimetric peak at 240°C to low temperature satellite peak at 140°C) reduces with an increasing number of annealing cycles in the temperature range from 350°C to 425°C.No significant change was observed in TL emission and ESR spectrum of the phosphor. The study shows that the annealing treatment in the temperature range from 600°C to 650°C could be the best alternative for annealing and re-use of CaSO4:Dyphosphor or a temperature below 350°C for Teflon embedded dosemeters.