The invention discloses an aluminum alloy metallographic corrosion method and a metallographic corrosive agent thereof. The metallographic corrosion method comprises the following steps that a, a 7055 aluminum alloy sample is subjected to pre-cleaning, hot inlaying, mechanical grinding and mechanical polishing treatment, washed with clear water and blow-dried, and then a metallographic sample is obtained; b, sequentially adding nitric acid, hydrochloric acid, sulfuric acid, hydrofluoric acid and deionized water into a container, and mixing to obtain a metallographic corrosive agent, wherein the metallographic corrosive agent comprises the following components in percentage by volume: 4-5% of nitric acid, 2-3% of hydrochloric acid, 1.5-2.5% of sulfuric acid, 2.5-3.5% of hydrofluoric acid and the balance of deionized water; and c, pouring the metallographic corrosive into a culture dish, placing the culture dish in a constant-temperature environment of 22-28 DEG C, immersing the metallographic sample into the metallographic corrosive, corroding for 25-35 seconds, taking out, washing, drying, and observing. The corrosion method is simple, the corrosion time is short, the effect of the metallographic corrosive agent is fully exerted, and the crystal boundary and crystal grains of the 7055 aluminum alloy are clearly displayed.