The invention relates to a metallographic corrosive agent and a corrosion method for a titanium-steel composite material and mainly aims at the metallographic corrosion of the titanium-steel composite material. The corrosive agent comprises the following components by weight proportion: 5-10 mL of hydrofluoric acid, 1-3 mL of nitric acid, 1-5 g of potassium fluoride (or sodium fluoride) and 80-100 mL of water. According to the metallographic corrosive agent and the corrosion method for the titanium-steel composite material provided by the invention, the metallographic corrosion of titanium can be conveniently and quickly realized, and steel is weakly corroded or is not corroded, so that the interference to over-corrosion caused by existing titanium and an existing titanium alloy corrosive agent to the steel is effectively avoided.