In this paper, the multichannel filtering properties caused by the dielectric defect layer of the one-dimensional magnetized plasma photonic crystal (PPC) in the terahertz band are studied by the transmission matrix method (TMM). The structure of (AC)N(CBC)M(AC)N is proposed, in which A is the plasma layer, B is the dielectric defect layer, C is the ordinary dielectric layer, N and M are the periods of the plasma layer and the dielectric defect layer respectively. The research shows that the filter channel generated by the structure is equal to M, and the variation of N will affect the photonic band gap (PBG) range. Secondly, the length of each layer will affect the frequency and transmission of the channel. In particular, the length of the C layer only affects the frequency of the channel and rarely affects the transmission. The refractive index of dielectric layer B affects both transmission and channel frequency. Thirdly, the increase of the plasma density causes the attenuation of the channel transmission, but rarely affects the channel frequency. The magnetic field range of PBG can be changed by controlling the plasma density. Therefore, this paper can provide ideas for the design of multi-channel tunable terahertz filter.