Embodiments of the present invention provide a method and an apparatus for reducing power consumption of a mobile phone and also a mobile phone. The method includes: activating a proximity sensor of a mobile phone when a call is originated or received; obtaining a weighted acceleration of the mobile phone by using an acceleration sensor; determining a switch-on time point of the proximity sensor according to the weighted acceleration of the mobile phone; and switching on the proximity sensor at the switch-on time point so that a backlight of the mobile phone is turned on or off according to a detection result of the proximity sensor. In the embodiments, in a conversation process of the mobile phone, a switch-on time point of a proximity sensor is obtained according to a weighted acceleration of the mobile phone, and the proximity sensor is switched on according to the switch-on time point to detect whether the mobile phone is approaching or leaving a human face. In this way, an appropriate switch-on time point may be obtained according to different weighted accelerations of the mobile phone, so as to reduce power consumption of the mobile phone in a conversation.