By the Green's function technique, we obtain the analytic expressions of the effective magnetoelectric property of composites and calculate the effective magnetoelectric properties of the threephase particulate composites made of rare earth-iron alloys, piezoelectric ceramics and polymer (Terfenol-D/PZT/PVDF). Our results show a strong influence of composite microstructure including the phase composition, aspect ratio of particles, orientation of polarization in PZT particles and applied bias field on the magnetoelectric properties. These numerical results provide guidelines for experimental design of the composites. After optimum design, the magnetoelectric voltage coefficient of these composites may reach as high as hundreds mV/A. As a new kind of magnetoelectric composite, such three-phase composites are expected to be a novel important kind of magnetoelectric materials because of their good magnetic-electrical response and easy fabrication.