Precise timing is a significant issue for an assisted-GPS receiver, time-tag of better that 10 milliseconds accuracy has typically been a requirement, and a high speed wireless link is generally used to offer this time-tag. A method is proposed to determine position and correct local clock of an A-GPS receiver, using a coarse time-tag of 10 seconds accuracy. The method firstly measures ≥5 in-view satellites' C/A code phases, then searches along the time axis to find out the time point matching the measured C/A code phases mostly, and simultaneously determines the receiver position. In the following several hours, only 4 satellites are necessary for positioning, until the local clock error exceeds the permission. By this method, requirement of extra hardware or high speed wireless link is eliminated, thus effectively decreased the complexity and cost of the receiver and the wireless link.