Abstract: For millimeter-wave high precision radar detection application, a six-port network circuit based on microstrip double ridge gap waveguide ( M-DRGW) has been proposed in this paper. The key circuits of power divider and coupler are designed based on the M-DRGW, and a novel transition between M-DRGW and microstrip is designed. The M-DRGW Ka-band six-port network is constructed based on the above circuits according to the simplified six-port network diagram. The measured results show that within the designed frequency range 37.5 GHz~42.5 GHz the phase differences between port 1/ port 2 and the other four output ports are, respectively, within ±2.5° and ±5°, and the insertion loss is about 7.3 dB at the middle working frequency. There is a consistence between the measured results and the simulated ones.