An automatic lighting system, comprising a plurality of sensing lighting devices, wherein each sensing lighting device comprises a light source module, a control module, a communication module and a sensor module, wherein all communication modules are configured to a same communication network; wherein each sensor module is configured to detect whether someone or something is within its respective detection range and to generate an effective signal if someone or something is detected; characterized in that each control module is configured to: receive the effective signal from the respective sensor module of the same sensing lighting device and, if the effective signal from the respective sensor module of the same sensing lighting device is received, to send the effective signal to the communication network through the communication module; receive an effective signal present in the communication network through the communication module; control the brightness of the respective light source module of the same sensing lighting device to maintain a first brightness if the effective signal is received from the respective sensor module of the same sensing lighting device or the communication network; and control the brightness of the respective light source module of the same sensing lighting device to maintain a second brightness less than the first brightness after no effective signal is received from the respective sensor module of the same sensing lighting device or the communication network. wherein each sensor module is configured to detect whether someone or something is within its respective detection range and to generate an effective signal if someone or something is detected; characterized in that each control module is configured to: receive the effective signal from the respective sensor module of the same sensing lighting device and, if the effective signal from the respective sensor module of the same sensing lighting device is received, to send the effective signal to the communication network through the communication module; receive an effective signal present in the communication network through the communication module; control the brightness of the respective light source module of the same sensing lighting device to maintain a first brightness if the effective signal is received from the respective sensor module of the same sensing lighting device or the communication network; and control the brightness of the respective light source module of the same sensing lighting device to maintain a second brightness less than the first brightness after no effective signal is received from the respective sensor module of the same sensing lighting device or the communication network. receive the effective signal from the respective sensor module of the same sensing lighting device and, if the effective signal from the respective sensor module of the same sensing lighting device is received, to send the effective signal to the communication network through the communication module; receive an effective signal present in the communication network through the communication module; control the brightness of the respective light source module of the same sensing lighting device to maintain a first brightness if the effective signal is received from the respective sensor module of the same sensing lighting device or the communication network; and control the brightness of the respective light source module of the same sensing lighting device to maintain a second brightness less than the first brightness after no effective signal is received from the respective sensor module of the same sensing lighting device or the communication network.