Abstract:  There may be several channels for the navigation signal to propagate from the satellite to the user, of which the group delay characteristics influence the zero value of time delay estimation. It is common practice to simply add the zero value of each channel to obtain zero value of cascaded channel, whether the sum of the zero values of each channel is simply equal to the zero value of the cascade channel has not been studied yet. In this paper, the influence of the group delay characteristics on the zero value is analyzed quantitatively. And the superposition characteristic of the zero value of time delay estimation under the cascade channel is estimated. The result of the simulation is verified on the software receiver. The results show that when the zeroorder group delay channel is equal to zero, it satisfies the superposition characteristic too. For other situations, the zero value does not satisfy the superposition characteristic, while the zero value can be approximately to satisfy it when the group delay coefficient is constrained.