The invention discloses a dual metal joint interface metallographic etching agent and a display method. The dual metal joint interface metallographic etching agent comprises the following components: a first etchant which is a mixed solution prepared from 6-10% of H2O2 water solution and 27% of ammonia water according to the volume ratio of 1 to 1, a saturated aqueous solution with 0.5-1 ml of potassium dichromate, and a second etchant which is 4-6% of HNO3 anhydrous ethanol solution by volume. The method comprises the steps of: sampling, preparing a sample, preparing an etching reagent, and displaying and obtaining a metallographic structure map of the sample. The agent disclosed by the invention is easily prepared; a copper and copper alloy/steel dual metal composite material joint interface structure can be rapidly and clearly displayed; and test and analysis of related performances of the novel composite material can be accurately carried out. By adopting the dual metal joint interface metallographic etching agent, performance improvement and failure analysis inspection abilities of a dual metal composite material member can be improved; and the etching agent has important directive significance on production and use.