An automatic sensing system includes at least one LED lamp, and at least one sensing control device. Each of at least one LED lamp includes at least three operation modes. The three operation modes includes a closing mode, a low light mode, and a fill light mode. The sensing control device includes an illumination detecting module, a pyroelectric sensing module, a signal processing module, and a lamp control module. The signal processing module is configured for processing the signal data output from the pyroelectric sensing module based on the signal data detected by the illumination detecting module and outputting a control signal. The lamp control module is configured for controlling all of the LED lamps to work in one of the three operation modes so as to make any one of the at least one sensing control device to control all of the LED lamps to work. The invention further includes an automatic sensing control method for LED lighting.