The invention proposes a lane keeping assist system and a lane keeping assist method. The method comprises the steps of comprehensively detecting a people-vehicle-road driving environment through a lane environment detection module, a vehicle state detection module, a driver driving state detection module and a vehicle and road surface rolling friction coefficient detection module; calculating a corresponding detection signal through a lane keeping control module; judging whether a vehicle deviates from a lane or not; performing transverse lane return-to-center control through cooperative control of an electric power steering system (EPS) and an electronic stability program (ESP), and keeping a longitudinal safety distance through ESP control; and giving an alarm for reminding. Through the technical scheme provided by the invention, the driving safety of vehicle driving is remarkably improved; and the lane keeping is realized through the cooperative control of the EPS and the ESP, so that on the premise of ensuring the driving safety of the vehicle, the working comfort of the lane keeping assist system can be improved to the maximum extent.