Composite powder material of the Y3Fe5O12-nSiC system was synthesized by a reverse coprecipitation method to study its heat generation property in an AC magnetic field. For Y3Fe5O12 (n = 0), the maximum heat generation ability of 0.45 W.g(-1) in an AC magnetic field (370 kHz, 1.77 kA.m(-1)) was obtained for the sample calcined at 1100 degrees C. The SiC addition helped to suppress the particle growth for Y3Fe5O12 at the calcination temperature. The heat generation ability was improved by the addition of the SiC powder, and the maximum value of 0.93 W.g(-1) was obtained for the n = 0.3 sample calcined at 1250 degrees C. The heat generation ability and the hysteresis loss value were proportional to the cube of the magnetic field (H-3). The heat generation ability (W.g(-1)) of the Y3Fe5O12-0.3SiC sample calcined at 1250 degrees C could be expressed by the equation 4.5x10(-4).f.H-3 using the frequency f(kHz) and the magnetic field H(kA.m(-1)).