A trace control system for an intravenous drip includes a housing having an inlet and an outlet. A cover is mounted to a side of the housing. The cover and the housing together define a receiving space. The inlet and the outlet are provided on an outer periphery of the housing and intercommunicate with the receiving space. A shaft unit is received in the receiving space. An impeller is coupled to the shaft unit and includes at least one vane. At least two magnetic elements are provided on the at least one vane. A magnetically inductive actuator is mounted to the outer periphery of the housing and detects the at least two magnetic elements. A controller is coupled to the magnetically inductive actuator and controls operation timing of the magnetically inductive actuator.
