The invention relates to a light-emitting 
diode (LED) dimming driving 
system with a 
silicon controlled bypass dimming circuit. The LED dimming driving 
system with the 
silicon controlled bypass dimming circuit comprises an 
alternating current / 
direct current (AC / DC) LED 
constant current actuator and a LED light string, wherein the input end of the AC / DC LED 
constant current actuator is electrically connected with an 
alternating current electric supply, the output end of the AC / DC LED 
constant current actuator is connected with the LED light string, the 
silicon controlled bypass dimming circuit is arranged, the input end of the silicon controlled bypass dimming circuit is connected with the 
alternating current (AC) electric supply, and the output end of the silicon controlled bypass dimming circuit is connected with a dimming interface of the AC / DC LED constant current actuator. The AC / DC LED constant current actuator obtains energy from the AC electric supply, and outputs a constant current value to drive the LED light string. The AC / DC LED constant current actuator is provided with an analog dimming interface which is used for adjusting an output current value according to an analog 
voltage amplitude value of an input dimming 
signal so as to change luminance of the LED light string. According to the silicon controlled bypass dimming circuit, the input end of the silicon controlled bypass dimming circuit is connected with the AC electric supply, and the output end of the silicon controlled bypass dimming circuit generates a smooth 
direct current analog 
voltage signal to serve as a dimming 
signal which is input into the analog dimming interface of the AC / DC LED constant current actuator. The value of amplitude of the dimming signal output by the silicon controlled bypass dimming circuit can be adjusted by adjusting an adjustable knob of the silicon controlled bypass dimming circuit, and thus a current value and the luminance of the LED light string can be adjusted.