The effects of the annealing time on the microstructure and magnetic properties of Dy0.5Fe60Pt39. 5 were investigated. X-ray diffraction and M-T data indicated that the disordered face-centered-cubic phase (soft phase) is not truly disordered phase due to an increase in the degree of short-range order with increasing of annealing time. Both the coercivity and remanence ratio of the FePt based alloy are as a function of the annealing time. The optimum heat treatment condition for the alloy is at annealing temperature of 600 °C for 5 h. These results of magnetic properties can be explained on the basis of phase transformation and microstructure of the alloy.