Multipactor is a critical reliability issue in space high-power microwave systems caused by secondary electron emission (SEE) avalanche. This effect degrades the performance of microwave component, or even cause failure of spacecraft in severe cases. Dielectric-filled microwave components, known for their high Q factor, low loss, and ease of miniaturization, are increasingly employed in space microwave systems. However, introducing dielectric in microwave components makes multipactor evolution more complexity since SEE process induces charge accumulation on dielectric surface and further affects the electron trajectory. In this work, by taking microwave ridge waveguide devices filled with polytetrafluoroethylene (PTFE) and polyimide (PI) as the research objects, we conducted device design, modeling, and multipactor evolution research. The physical mechanism of SEE avalanche for the dielectric microporous structures was analyzed. The theoretical results demonstrated that constructing microporous structures on the dielectric surface can effectively reduce the SEE yield (SEY) and significantly enhance the device's multipactor threshold. Then periodic microporous arrays were fabricated on PTFE and PI surfaces using femtosecond laser processing. SEY testing results showed that after constructing surface microporous, the peak SEY of PTFE decreased from 2.1 to 1.4, a reduction of 33.3%, while the first crossover energy (E_P1) increased from 40 eV to 95 eV. And for PI, after constructing surface microporous, the peak SEY decreased from 1.4 to 1.1, a reduction of 21.4%, and E_P1 significantly increased from 65 eV to 205 eV. The microporous structure raised the multipactor thresholds of PTFE- and PI-filled single-ridge waveguides to 12374 W and 12109 W, respectively, representing an improvement of approximately 5000 W compared to original devices’ multipactor thresholds of 7734 W and 7265 W. This research provides an effective approach for microstructural treatment of dielectric surfaces in high-power microwave devices, and holds significant engineering application value for anti-multipactor designs in various microwave systems.