A method and system for turning off an alarm of a mobile terminal, by presetting an area threshold value, includes automatically turning on the mobile terminal's screen when the alarm of the mobile terminal sets off and detecting if a touch signal is inputted. When a touch signal is inputted, calculating an area of a valid touch region in which a user touches the touchscreen and comparing the calculated area of the valid touch region with the area threshold value. If the area of the valid touch region is greater than or equal to the area threshold value, controlling the mobile terminal to turn off the alarm. If the area of the valid touch region is smaller than the area threshold value, the alarm of the mobile terminal keeps ringing.