The invention relates to a sea surface floating oil detergent and a preparation method thereof, belonging to the technical field of detergents. The sea surface floating oil detergent is prepared from the following raw materials in parts by mass: 20-30 parts of activated carbon, 5-10 parts of polyacrylamide, 12-20 parts of outer bran, 30-40 parts of vermiculite, 2-7 parts of soybean protein, 2-4 parts of N,N-dimethyldecyl amide, 0.5-1 part of alkane oxidation bacterium, 1-2 parts of Epipremnum Aureum and 12-17 parts of water. The sea surface floating oil detergent is simple in preparation method, can effectively remove marine floating oil, and has favorable cleaning action. By adopting the environment-friendly raw materials, the sea surface floating oil detergent has higher self degradation ratio after use, can not cause secondary pollution to the sea area, and is easy for popularization and application.