An automatic toilet seat cleaning system including a movable toilet seat supported on a toilet bowl of a toilet in front of a toilet water tank and moved between a front side position and a rear side position, a fixed first motor, a transmission mechanism controlled by the first motor to turn the toilet seat horizontally when the toilet seat is moved to the rear side position, a fixed second motor, a wheel brush turned by the second motor to clean the toilet seat when the toilet seat is moved to the rear side position and turned by the transmission mechanism, a waste water tank adapted to hold waste water falling from the movable toilet seat, a water tube adapted to guide clean water to the wheel brush for cleaning the toilet seat, and an electrical dryer controlled to dry the toilet seat.