In view of the large dynamic and fast acquisition requirement of inter-satellite links (ISLs) signal, a capture initial information solution method is presented for ISLs of navigation constellation. This method evaluates time-delay and Doppler frequency based on ephemeris. The analysis shows that this method has a simple realization process, a high speed of restraining and a high precision of evaluation, and can achieve the degree of nanosecond for the time delay through merely two times of iteration, which has greatly reduced the computing difficulty and complexity. This analysis is made upon the model of BeiDou navigation system and can provide reference for our country’s ISLs design.