A relay diagnosis circuit, diagnosis method, and battery management system are disclosed in the present disclosure. The relay diagnosis circuit may include a first sampling unit, a second sampling unit, a first sampling point, a second sampling point, a reference voltage terminal, and a processor. A first end of the first sampling unit is connected with voltage output end of the power battery pack to be measured and a first end of a relay. A second end of the first sampling unit is connected with the reference voltage terminal and the first sampling point. A first end of the second sampling unit is connected with a second end of the relay. A second end of the second sampling unit is connected with the reference voltage terminal and the second sampling point.