For improving efficiency of band-limited Gaussian noise jamming, this paper uses code tracking error and ephemeris bit error rate of global positioning system(GPS) receiver as the jamming effect evaluation index. Combining GPS P(Y) code and M code signal power spectrum characteristics, the optimal jamming bandwidth is derived theoretically and calculated quantitatively under different jamming to signal ratio and subcarrier modulation phase respectively. The power synthesis of distributed band-limited Gaussian noise jamming sources which are to be adopted is discussed. It is concluded that increasing the number of jamming sources can reduce the relative loss of synthetic power; however, it will improve the risk probability of appearing small values. Therefore, it should set optimal jamming bandwidth based on the actual power synthesis expectations, and select number appropriate and power random distributed band-limited Gaussian noise jamming sources to achieve the purpose of improving jamming efficiency.