A method for tracking a satellite signal by a GPS includes the following steps. Data is continuously received from one of satellites by using tracking frequencies updated one by one based on an average phase difference of received data. Phase inversion points in the plurality of received data are interpreted. A time difference between each two adjacent phase inversion points among the phase inversion points is calculated. It is determined whether each time difference is an integral multiple of 20 ms. When each time difference is an integral multiple of 20 ms, 1-bit data is retrieved for every 20 ms from the satellite signal by taking a first phase inversion point among the plurality of phase inversion points as a starting point. Thus, a positioning speed is increased and a required positioning time is reduced by finding out a precise tracking frequency and a correct phase inversion point.