On-chip filters are widely used in integrated optical systems and are indispensable for expanding the communication capacity. A silicon waveguide filter is fabricated into a subwavelength Bragg grating structure using the optical phase-change material Ge₂Sb₂Se₄Te₁ (GSST). Three-dimensional finite-difference time-domain method simulations showed that this structure performed multichannel filtering in the communications C-band (1530 to 1565 nm), demonstrating a minimum insertion loss of 0.238 dB and a full width at half-maximum of 3.4 nm with an incident TE0 mode. The number and width of channels can be adjusted using structural parameters. Furthermore, the overlapping frequencies of passbands and stopbands are obtained by the phase transition of GSST. This structure could potentially find use as an optical signal modulation device in on-chip integrated systems.