In this paper, the controllability problem was studied for multi-agent systems under leader-follower structure. The contribution includes: (i) the controllability analysis for a kind of directed interconnection topology, i.e, the so-called non-fully symmetric (NFS) directed interconnection graph; (ii) the presentation of some connections between controllability and consensus; (iii) the changing of a class of uncontrollable undirected interconnection graph into a controllable one by assigning weights between agents. Also, the selection of leaders is discussed. Several examples are given to illustrate the ideas and the corresponding results.