The invention discloses a method for consolidating soft soil foundation by using vacuum and magnetic field compound preloading. The action of a magnetic field is introduced into vacuum preloading and surcharging processes, and the vacuum preloading, the magnetic field and surcharging preloading are conducted simultaneously, so that the action time is not required to be exerted independently, the construction period and the cost are saved, and the consolidating effect can be improved. The magnetic field induces water to generate molecular sensing magnetic torques, and the interaction of the molecular sensing magnetic torques can change the viscosity of water in the soil, increase the diffusion and permeation speeds of the water and promote the permeability of the water effectively; and the magnetic field can not only act on free water in the soil, but also act on bound water to enable the water to be free from constraint and drained in a certain direction in a permeating manner, so that a consolidating purpose is achieved. The magnetic field can also change certain physical properties of soil particles, such as the caking property, the swelling amount, the surface tension, the aggregation function and the like; and a consolidating function can be reinforced, the consolidating speed can be increased, and manpower and material resources consumed in foundation processing are saved by the aid of the fact that the magnetic field can facilitate drainage consolidation.