Multipactor breakdown analysis is presented in cylindrical dielectric resonator waveguide filter under its dual-mode behavior. The method of effective electron algorithm with combination of Monte-Carlo method is used to perform the simulation and predict multipactor breakdown thresholds. The breakdown thresholds of the proposed structure are presented for different values of frequency-gap product. The results indicate that increasing the radius of filter increases the RF breakdown threshold. The results are compared with the classic parallel plate waveguides.