The E-band broadband high-Intermediate Frequency(IF) single balanced mixer is proposed to meet the demand of the communication, radar and test instruments in the millimeter-wave broadband field. The Radio Frequency(RF) and Local Oscillator(LO) signals are input through the multi- branch broadband broadened waveguide quadrature coupler. The signal is transitioned from the waveguide transmission mode to the microstrip mode through the grounding fin transition structure, providing a broadband IF signal loop and DC grounding. The IF output low-pass filter can effectively suppress the LO and RF signals and provide an equivalent grounding circuit for them. The mixer employs the nonlinearity of the Schottky barrier diode to achieve mixing, and ultimately achieves a wideband low- loss mixing effect through the microstrip matching circuits. The mixer utilizes three LO frequencies of 57.6 GHz, 62.4 GHz, and 67.2 GHz to segmentally down-convert the RF signal within the range of 67~ 85 GHz to the IF range of 9.4~ 17.8 GHz. The test results indicate that within the 67~85 GHz RF range, when the RF input power is -15 dBm and the LO input power is 12 dBm, the frequency conversion loss of the mixer is 7. 1~ 10. 1 dB, and the undesired mixing product rejection is above 36 dBc.