Abstract: A control strategy of acquisition and tracking for code loop and carrier loop is designed to detect GPS signal. Sequential searching scheme and narrow space non-coherent digital delay locked loop assure reliable acquisition and precise tracking for code phase. Integrated algorithms of 4-quadrant frequency, cross-product automatic frequency control and Costa phase locked loop are adopted to speed up frequency acquisition and effectively track carrier frequency/phase changing, and therefore obtain better dynamic and noise performance. The control algorithms and loop parameters determination are implemented by software with inflexibility. Digital system based on spread spectrum correlator and digital signal processor proved above scheme be correct and efficient.