When the vehicle is traveling at hypersonic speeds or during re-entry, the surface is enveloped by a plasma sheath. Plasma sheath can impede electromagnetic wave propagation, causing vehicle radio signals to be attenuated or even interrupted, which is communication blackout. The traveling magnetic field is a kind of magnetic field that can mitigate the communication blackout by regulating the density of the plasma sheath. In this paper, a three-dimensional traveling magnetic field generation model and a three-dimensional plasma density distribution model are established for the problem that the one-dimensional traveling magnetic field cannot accurately describe the plasma density distribution in space. The mechanism of the interaction between the traveling magnetic field and the plasma was investigated to obtain the plasma density distribution in space. The results show that the application of a traveling magnetic field is capable of generating a density reduction region with dimensions of 50 $\times$ 100 mm at the rear end of the vehicle, reducing the density of the inhomogeneous plasma in the region by a maximum of 71% and providing sustained communication time. Meanwhile, the effects of initial density, collision frequency, traveling velocity and current magnitude on the plasma density distribution were investigated. The results show that with the increase of the initial density, the ability to regulate the plasma density is improved, but due to the large density base, the regulated plasma density is still higher than that of the low-density case; the increase of the collision frequency significantly reduces the regulation effect; the increase of the traveling velocity and the current are able to enhance the density regulation effect, but continuing to increase the traveling velocity on the basis of 800 m/s does not produce a more significant regulation effect. Based on the data from the RAM-C flight test, the effects of current magnitude and traveling velocity on the electromagnetic wave attenuation during the reentry process of the vehicle are investigated using the proposed model, and the mitigation effects of the traveling magnetic field on the electromagnetic wave attenuation are also compared with those of the applied static magnetic field. The results show that the applied traveling magnetic field can reduce the electromagnetic wave attenuation of the vehicle to less than 30dB in the X-band at 30.48km, as well as in the L-, S-, C- and X-bands at other altitudes. The comparison results of traveling magnetic field and static magnetic field show that the mitigation effect of traveling magnetic field on electromagnetic wave attenuation is significantly better than that of static magnetic field.