The invention discloses a PWM-based voltage diming LED control system. An LED slave circuit module in the system mainly comprises a voltage conversion module, a PWM generation module and a drive line which are electrically connected in sequence, wherein the LED dimming principle is that an input voltage value of an LED slave circuit is firstly changed directly according to the brightness requirement on an LED, and a PWM signal, for driving a switch tube, of the LED slave circuit is changed or current flowing through the LED is stabilized at a corresponding value after the LED slave circuit passes through the voltage conversion module, thereby changing the brightness of the LED. Compared with an existing LED dimming technology, the PWM-based voltage diming LED control system has the beneficial effects that the LED dimming target can be achieved without arranging a communication module or arranging a peripheral circuit or control chip of generating the PWM signal, and meanwhile, constant-current dimming of the LED can be achieved.