The invention relates to the technical field of oil pollution cleansing agent accessory devices, in particular to a heavy oil pollution cleansing agent and a preparation method thereof. The heavy oilpollution cleansing agent comprises, in 100 parts by weight, 2-5 parts of potassium carbonate, 3-6 parts of sodium carbonate, 2-4 parts of potassium silicate, 3-6 parts of tetrapotassium pyrophosphate, 10-30 parts of surfactants, 5-10 parts of solubilizers, 1-4 parts of sterilizing preservatives, 4-8 parts of lipase and 27-70 parts of deionized water. The preparation method of the heavy oil pollution cleansing agent includes the steps: (1) pre-mixed solution preparation; (2) surfactant addition; (3) solubilizer addition; (4) lipase and sterilizing preservative addition.