The needs of scientific targets of the low-low satellite-to-satellite tracing （SST-LL） gravity exploring satellite for the orbit life, ground-coverage, altitude variation range in one circle and distance between two satellites are considered. According to the needs, the aerodynamic loss and the optimal in- clinations are computed. As a result, the initial altitude should be 500kin and inclination of 89°would be the best choice for the ground-coverage and launch vehicle. The altitude variation range is less than 50km with the eccentricity 0. 0020. The main cause of the distance variation between two satellites is aerody- namic drag, and the control strategy of the distance variation is analyzed, such as periodic orbit maneuver for the satellite which sufferes higher aerodynamic drag.%论述了SST-LL重力测量卫星科学任务对轨道寿命、地面覆盖性能、轨道高度单圈波动、星间距离变化范围的需求。根据需求，计算了轨道的自然衰减情况，得l出轨道初始高度为500km；综合考虑地面覆盖要求及运载火箭能力，得出了最佳轨道倾角为89°；得出了0．0020偏心率下轨道高度波动范围不超过50km；分析得出星间距离的长周期变化主要受大气阻力影响，初步确定了轨道控制方案，即定期对受大气阻力较大的卫星进行轨道机动。
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