The galvanic corrosion of SS 304-Al 6061 in 30% nitric acid environment and the influence of different area ratios of cathode and anode on the corrosion process of SS 304-Al 6061 were studied by immersion and electrochemical experiments. The surface morphology, number of corrosion pits and electrochemical parameters of Al 6061 before and after corrosion were measured and analyzed by means of SEM, EDS and electrochemical measurement. The results show that the corrosion driving potential difference between Al 6061 and SS 304 reaches 583 mVSCE, and Al 6061 is used as the reaction anode to dissolve corrosion. It can be seen from SEM images that there are three kinds of galvanic corrosion phenomena after coupling, among which the micro-galvanic corrosion caused by the second phase particles coupled with the aluminum matrix is the main type of corrosion pits. Meanwhile, the increase of the area ratio of cathode and anode leads to the decrease of the galvanic potential and the increase of the corrosion current. The galvanic current and the area ratio of cathode and anode satisfy the quantitative relationship, and the theory is in good agreement with the practice by K-S test.