With the urgently increasing demand for high-speed and large-capacity communication transmission, there remains a critical need for tunable terahertz (THz) devices with multi-channel in 5G/6G communication systems. A magnetic phase-coding meta-atom (MPM) is formed by the heterogeneous integration of La:YIG magneto-optical (MO) materials and Si microstructures. The MPM couples the magnetic induction phase of spin states with the propagation phase and can simultaneously satisfy the required output phase for dual frequencies under various external magnetic fields to realize the dynamic beam steering among multiple channels at 0.25 and 0.5 THz. The energy ratio of the target direction can reach 96.5%, and the nonreciprocal one-way transmission with a max isolation of 29.8 dB is realized due to the nonreciprocal phase shift of the MO layer. This nonreciprocal mechanism of magnetic induction reshaping of wavefront significantly holds promise for advancing integrated multi-functional THz devices with the characteristics of low-crosstalk, multi-channel, and multi-frequency, and has great potential to promote the development of THz large-capacity and high-speed communication.