The method and experimental process to calibrate the energy of electron beam by resonant depolarization is discussed in this paper. As a characteristic function of spin dynamics, spin response function is an indispensable parameter of depolarization time. The spin response function at Hefei electron storage ring was calculated, and the result of spin response function in a period of the ring was presented. In the experiment of spin depolarization to calibrate HLS beam energy, the spin response function in the position of depolarization is 1.569 m, and the depolarization time is 60 s.