The invention relates to a sensing method of a sensor, which carries out detection by a driving detection mode and a driven detection mode. The driving detection mode can detect an environment background in advance, and an original environment parameter is temporarily stored. Under the action of the driven detection mode, the driving detection mode is intermittently carried out, and a condition whether a subsequent device is activated or not can be determined according to a detection result of the driven detection mode, or a detection result of the driving detection mode is compared with the original environment parameter to determine whether the subsequent device is activated or not.