The invention relates to a preparation method for an alternating frequency ultrasound coupling hot-pressing infiltration porous ceramic enhanced magnesium matrix composite material, and relates to a preparation method for the magnesium matrix composite material. The preparation method solves the technical problems that an existing ceramic enhanced magnesium matrix composite material is low in plasticity and poor in forming capacity. The preparation method comprises the steps that a combination of a porous ceramic clad magnesium alloy melt is prepared through alternating frequency ultrasound coupling hot-pressing quick molding; and temperature rise mechanical stirring is carried out under the alternating frequency ultrasound vibration effect, and alternating frequency ultrasound coupling hot-pressing quick molding is carried out. According to the preparation method, through alternating frequency ultrasound coupling hot-pressing quick molding, alternating frequency ultrasound treatment can improve the magnesium liquid infiltration capacity, the temperature rise mechanical stirring facilitates diffusion and improves the structure homogeneity, the hot-pressing quick molding can reducecasting flaws, refine grains and improve distribution of a second phase, and the obdurability of the porous ceramic enhanced magnesium matrix composite material can be obviously improved under the effect of alternating frequency ultrasound coupling hot-pressing quick molding.