In order to get different harmonics output of frequency multiplier, a 170 GHz and 340 GHz frequency selective network based on Compact Suspended Microstrip Resonators(CSMRs) filter was designed. The design met the multi-frequency requirements of systems, and the cost was reduced and the system integration degree was increased. In the simulation, the 170 GHz and 340 GHz probes were designed respectively. CSMRs low-pass filter was introduced to increase the isolation degree of 170 GHz and 340 GHz bands. The waveguide height was decreased, the cutoff frequency of the WR.2.8 waveguide was increased below 300 GHz. The measurement module was back-to-back of Selective Network. The simulation results show that CSMSRs filter has S11<-18 dB between 20 GHz and 180 GHz, S12<-20 dB between 266 GHz and 520 GHz. The back-to-back module S11 is better than -15 dB at 170 GHz and 340 GHz bands, and two ports isolation degree is better than 30 dB. Measurement results show that S11<-10 dB and transmission loss is better than 1.2 dB at 150-185 GHz. S11<-10 dB between 306 GHz and 355 GHz, and transmission loss is 2 dB, two ports isolation degree is 10-60 dB.