The invention belongs to the technical field of sludge. The invention provides an oily sludge treatment agent for an oil production plant. The main raw materials are as follows in parts by weight: 3-5parts of saccharin sodium, 16-21 parts of montmorillonite, 7-18 parts of polyoxyethylene, 5-15 parts of humic acid, 0.5-1.3 parts of maleic anhydride, 7-10 parts of sodium bicarbonate, 3-7 parts of mozzie buster, 0.5-0.8 part of polyaluminum chloride, 8-13 parts of waste coconut peel, 2-7 parts of finger citron and 15-20 parts of chitosan. The invention relates to a preparation method of the oilysludge treatment agent for an oil production plant, which comprises the following steps: (1) uniformly mixing the saccharin sodium salt, the montmorillonite, the polyoxyethylene, the mozzie buster, the maleic anhydride and coconut peel, grinding the mixture into powder, and mixing the powder to obtain particles; (2) uniformly mixing the particles with the sodium bicarbonate, the humic acid, the finger citron, the chitosan and the polyaluminum chloride, and stirring and mixing at 40-55 DEG C for 2-3 hours. The oily sludge treatment agent has the advantages of simple treatment process, small dosage, good treatment effect and stable performance.