Introducing InterSatellite Links (ISLs) is a major trend in new-generation Global Navigation Satellite Systems (GNSSs). Data transmission scheduling is a crucial problem in the study of ISL management. The existing research on intersatellite data transmission has not considered the capacities of ISL bandwidth. Thus, the current study is the first to describe the intersatellite data transmission scheduling problem with capacity restrictions in GNSSs. A model conversion strategy is designed to model the aforementioned problem as a length-bounded single-path multicommodity flow problem. An integer programming model is constructed to minimize the maximal sum of flows on each intersatellite edge; this minimization is equivalent to minimizing the maximal occupied ISL bandwidth. An iterated tree search algorithm is proposed to resolve the problem, and two ranking rules are designed to guide the search. Experiments based on the BeiDou satellite constellation are designed, and results demonstrate the effectiveness of the proposed model and algorithm.