In this article, we investigate the controllability of multi-agent systems with leaders as control inputs, where the interconnection is directed and weighted. We employ weight-balanced partition to classify the interconnection graphs, and study the controllable subspaces with given nontrivial weight-balanced partition. We also provide two necessary and sufficient graph conditions on structural controllability and strong structural controllability. Moreover, we consider the effect of the zero row-sum restrictions of the system matrices on structural controllability.