In this paper, we investigate a formation control problem of multi-agent systems (specifically a group of unmanned aerial vehicles) based on a semi-global leader-following consensus approach with both the leader and the followers subject to input saturation. Utilizing the low gain feedback design technique, a distributed static control protocol and a distributed adaptive control protocol are constructed. The former solves the problem under an assumption that the communication network is undirected, and it depends on the global information of the graph. For the latter, we relax the undirected graph to directed graph. Moreover, an adaptive updating gain is designed to avoid using the global information of the communication network. It is shown that the consensus protocols can solve the semi-global leader-following consensus problem if the leader agent is globally reachable. The results are verified successfully by both simulation and real flight tests.