Out-of-sight communication in ground-air communication is a difficult problem; especially the effective implement of the out-of-sight communication on fighters is more difficult. In order to implement ground-air out-of-light communication, a small single orbit satellite net is proposed. The orbit height of the small satellite is low, so both the communication link loss and the communication transmission time delay are smaller, thus, the requirement in quality for the antenna in fighters is decreased. In this way, it is possible to realize the direct communication between fighters and small satellites. Several satellites in one orbit grouping a net can realize continuous communication cover for parts of an area, so can satisfy the needs for the out of sight communication to parts of an area. The developing period for the small satellite is short, and the launching method of the small satellite is flexible. The orbit characters can also be designed according to the needs of the communication area. These characters of the small satellite accord with the military needs. In this paper, the orbit characters including the orbit height, the quantity of the small satellite, center departure rate, communication cover range, etc are studied.