The utility model provides a pretreatment system for kitchen waste sewage. The system comprises an adjusting tank, an oil separation cooling tank, a first coagulative precipitation tank, a second coagulative precipitation tank, a cavitation air floatation tank, a dissolved air floatation tank and a water outlet tank which are connected in sequence, the first coagulative precipitation tank is provided with a coagulant and flocculant dosing port, the second coagulative precipitation tank is provided with an alkali/demulsifier dosing port, and the water outlet tank is provided with an acid dosingport; and the oil separation cooling pool is provided with a cooling device. The technical scheme of the utility model is adopted; kitchen waste sewage is pretreated, the content of high suspended solids and high grease in the kitchen waste sewage is reduced, the kitchen waste sewage enters the leachate treatment system, biochemical unit collapse of the leachate treatment system and pollution blockage of a membrane system are avoided, the function of kitchen waste co-treatment of a household waste incineration power plant is better played, investment is reduced, and benefits are improved.