The invention discloses a passive wideband mixer, including a local oscillator balun, a radio frequency balun, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, an inductive compensation unit, and a lossy inductive grounding network. The invention can realize a mixer with a bandwidth ratio of not less than 1:7, and can effectively suppress points with isolation deterioration without affecting the conversion loss over the entire frequency band. In the entire frequency band of this design, the isolation indicator between the local oscillator and radio frequency ports is optimized, which can well satisfy the application of the wideband mixer in a communication system.