Provided are a system and a method for measuring a liquid level of a vehicle fuel tank, and more particularly, to a system for measuring a liquid level of a vehicle fuel tank including an ultrasonic sensor unit provided on a bottom surface in the vehicle fuel tank to acquire measurement data for calculating a distance from the bottom surface in the fuel tank to a fuel surface and a central processing unit using the measurement data transmitted from the ultrasonic sensor unit by a preset number of times for a preset time to calculate liquid level information of the fuel tank.