A LED driving circuit includes a DALI module, a linear voltage luminance adjusting module, a DIP luminance adjusting module, a control module, a power source, a constant current driving module and an output module. The DALI module generates a PWM signal. The linear voltage luminance adjusting module generates a second PWM signal. The DIP luminance adjusting module generates a switch signal. The control module generates a drive PWM signal using the first PWM signal, the second PWM signal and the switch signal. The power source provides power. The constant current driving module generates a constant-current drive voltage using the provided power and the drive PWM signal. The output module generates a drive current that responds to the constant-current drive voltage. And the output module drives an external LED device using the drive current.