A timing controller and an operation method thereof are provided. The timing controller includes a transmitter circuit and a control circuit. The control circuit ends a normal mode to enter a swing boost mode when a lock signal fed back by a source driving circuit indicates that quality of data signal is deteriorated in the normal mode. In the swing boost mode, the control circuit controls the transmitter circuit to boost the swing of the data signal from a normal level to a high level. The control circuit ends the swing boost mode and enters a clock training mode when the source driving circuit causes loss of lock to the data signal in the swing boost mode. In the clock training mode, the control circuit controls the transmitter circuit to employ a clock training data string as the data signal to transmit to the source driving circuit.