Three different designs of plasmonic photonic crystal filters (two-channel, three-channel, and four-channel) are proposed and considered. The photonic crystal structures consist of standing rods made of Ag and GaAs, whereby introducing different simple or ring-shaped defects, two-, three-, or four-port filters are realized. Optical fluid is used instead of air as the background material, owing to its versatile benefits. By utilizing different combinations of optical fluids and plasmonic materials, multichannel filters are obtained which can function better by improving the structural parameters such as the rod’s radius. Considering the four-port filter, its applications as the power splitter are also investigated. For tuning the filter properties such as the resonance peak’s value and wavelength, impacts of Ag and GaAs rod radius on the transmission spectrum are examined. The following resonance peak’s value and FWHM are obtained for the proposed structures: two-channel filter (0.9, 4 nm), three-channel filter (0.8, 2 nm), four-channel filter (0.5, 10 nm). The proposed designed filters can be utilized in the photonic integrated circuits as well as the nanophotonics devices for medical and industrial applications.