Herein, a filterless 24-tupling frequency millimeter-wave generator based on polarization multiplexing was proposed. The generator cascaded a three-parallel Mach-Zehnder modulator structure and a single Mach-Zehnder modulator. Further, the generator used the polarization multiplexing structure to filter out all redundant optical sidebands, leaving only 12th order optical sideband signals. The scheme can produce a 24-tupling frequency millimeter-wave signal without any optical or electrical filter. Moreover, combined with the theoretical study of the system, the feasibility of the generator was verified via simulation. The system performance was analyzed and the effects of modulation depth, extinction ratio, phase difference, bias voltage, and line width of the laser on system performance under non-ideal conditions were discussed. The research results show that the value of the optical sideband suppression ratio and radio frequency stray suppression ratio can reach 40 dB and nearly 30 dB, respectively. The system maintains good transmission performance for 150-km transmission distance. The system does not require any auxiliary filter. This system demonstrates the advantages of a high-frequency multiplier and good spectrum quality, thus providing important reference values for research of filterless millimeter-wave generator.