The invention discloses a firmware version updating method and system. The firmware version updating method comprises the steps that A, when a mobile terminal detects that newly-added firmware exists in a memory card or information of the newly-added firmware on a server is detected through a network, the information of the file size of the newly-added firmware is obtained; B, the obtained information of the file size of the newly-added firmware is compared with the information of the file size of current firmware which is stored in advance, judgment is conducted, and if the file size of the newly-added firmware is larger than that of the current firmware, the step C is executed; C, the firmware is updated with the newly-added firmware. According to the firmware version updating method and system, due to the fact that the correspondence relation between the firmware version and the file size of the firmware is set, the purpose that the firm version can be identified just according to the file size of the firmware in the process of updating the firmware is achieved, the problem that due to the fact that version information is stored, the file is increased or the newest firmware version cannot be obtained remotely is solved, and timely updating of the firmware is facilitated.