This paper mainly discusses the analysis and design of a finline single-ended mixer and detector.In the circuit,for the purpose of eliminating high-order resonant modes and improving transition loss,metallic via holes are implemented along the mounting edge of the substrate embedded in the split-block of the WG-finline-microstrip transition.Meanwhile,a Ka band slow-wave and bandstop filter,which represents a reactive termination,is designed for the utilization of idle frequencies and operation frequencies energy.Full-wave analysis is carried out to optimize the input matching network of the mixer and the detector circuit using lumped elements to model the nonlinear diode.The exported S-matrix of the optimized circuit is used for conversion loss and voltage sensitivity analysis.The lowest measured conversion loss is 3.52dB at 32.2GHz;the conversion loss is flat and less than 5.68dB in the frequency band of 29-34GHz.The highest measured zero-bias voltage sensitivity is 1450mV/mW at 38.6GHz,and the sensitivity is better than 1000mV/mW in the frequency band of 38-40GHz. This paper mainly discusses the analysis and design of a finline single-ended mixer and detector. In the circuit, for the purpose of eliminating high-order resonant modes and improving transition loss, metallic via holes are implemented along the mounting edge of the substrate embedded in the split-block of the WG-finline-microstrip transition. While the Ka band slow-wave and bandstop filter, which represents a reactive termination, is designed for the utilization of idle frequencies and operation frequencies energy. Full-wave analysis is carried out to optimize the input matching network of the mixer and the detector circuit using lumped elements to model the nonlinear diode. The exported S-matrix of the optimized circuit is used for conversion loss and voltage sensitivity analysis. dB at 32.2 GHz; the conversion loss is flat and less than 5.68dB in the frequency band of 29-34GHz. The highest measured zero-bias voltage sensitivity is 1450mV / mW at 38.6G Hz, and the sensitivity is better than 1000mV / mW in the frequency band of 38-40GHz.