The invention discloses an automatic hanging-up method, which comprises the following steps of: a, setting a hanging-up critical time; b, in a call of a mobile phone, clearing a value N of a timer; c, acquiring remote voices and local voices; d, calculating a remote voice parameter quantitative value and a local voice parameter quantitative value respectively; e, judging whether the local voices and the remote voices are all inactive frames or not according to the obtained remote voice parameter quantitative value and the obtained local voice parameter quantitative value, entering a step f if the local voices and the remote voices are all inactive frames, otherwise returning to the step b; f, setting the value N of the timer to be N+1; and g, when the time N of the timer is more than the set critical time, controlling the automatic hanging-up of the mobile phone. The invention also provides an automatic hanging-up system. By the method and the system, automatic hanging-up can be realized so as to avoid unnecessary wastes.