Abstract: Quick acquisition of satellites signals is a key technology in the assisted GPS (A-GPS) receiver. Considering that the A-GPS receiver can obtain the valid ephemeris data from the assistance data, a new estimate algorithm for pseudo-code phase delay and its uncertainty are proposed. On the basis of the Taylor approximation for the time of GPS signal transmission function, the estimate equation of pseudo-code phase delay and its uncertainty are proposed by using the assistance data. Simulation and experimental results show that the proposed algorithm can effectively compress the uncertainty of pseudo-code phase delay to the rest satellites, and can accelerate the signal acquiring speed of A-GPS receiver. As for the conventional un-assisted GPS receiver, the pseudo-code phase delay and its uncertainty can also be well estimated by the algorithm proposed in the paper when effective ephemeris data, satellite clock bias and pseudo-range amendment information are pre-stored in the receiver.