In recent years, the electrocaloric effect (abbr. ECE) of dielectrics has attracted attention for ferroelectric refrigerating application. The fundamentals of ferroelectric refrigeration and the expressions of three types of ECEs, i.e., linear, quadratic and field-induced first-order phase transition electrocaloric effects, are presented in this paper. The ECE properties of (1-x)PbMg1/3Nb2/3O3-xPbTiO3［abbr. (1-x)PMN-xPT］ ferroelectric ceramics(x=0.08, 0.10, and 0.25 respectively) at room temperature were measured and analyzed. It is found that the large electrocaloric effect of (1-x)PMN-xPT ferroelectric ceramics about room temperature is due to the electric-induced first-order phase transition and linear electrocaloric effects, and these ceramics could be used in ferroelectric multi-stage refrigeration.