This paper considers the formation control of large-scale fixed-wing UAV swarms, and proposes a group-based hierarchical method. Firstly, a distributed group-based control architecture is proposed for the UAV swarms, which divides all the UAVs into several distincts and non-overlapping groups, and the UAVs in each group are organized into two layers, the leader layer and the follower layer. Secondly, for leader UAVs, the coordinated path following control law is proposed, which steers the leader UAVs towards their virtual targets on their desired paths, and achieves the coordination of leader UAVs by coordinating the movement of the virtual targets, thus the inter-group coordination is achieved. Thirdly, a leader-following formation control law is proposed for the follower UAVs to follow the leader UAVs in their respective groups. The proposed formation control law for large-scale swarms considers the control constraints of fixed-wing UAVs and wind influence, and the closed-loop stability is theoretically guaranteed. Numerical simulations of 100 fixed-wing UAVs in a whole mission process are conducted, which validate the effectiveness of the proposed method for large-scale swarms.