Disclosed is a method of particle reinforced metal matrix composite continuous casting in compound magnetic field at different frequency, relating to material processing technology field; in the process of the preparation of the composites melt, low-frequency alternating magnetic field is applied: the frequency is from 5 to 50 Hz, the power range is from 5 to 60 kW; electromagnetic stirring is carried out, making the particles to be fined and evenly distributed; in the process of continuous casting, low-frequency alternating magnetic field is applied to the crystallizer zone: the frequency is from 5 to 50 Hz, the power range is from 5 to 20 kW; electromagnetic stirring is carried out to improve the internal quality; meanwhile, the high-frequency alternating magnetic field is applied in initial solidification zone in crystallizer: the frequency is from10 to 50 kHz, the power range is from 20 to 100Kw, soft contact is applied to improve the surface quality of casting billet. The composites article reinforcement prepared by the method are evenly distributed and fined, the internal organization is compact without any structural defects such as rarefaction or shrinkage hole, the casting billet has high surface finish without any defects.