An LED light string control system includes an LED light string, a voltage generation apparatus, and a control module. The control module controls the voltage generation apparatus to change a signal provided to the LED light string to a first voltage level according to a first logic of a light command, and to change the signal to a second to a second voltage level according to a second logic of the light command. The control module controls the voltage generation apparatus to change the signal to a distinction voltage once first logics and/or second logics of the light command appear consecutively.