The utility model relates to double coattail bases which include double seat bodies. The utility model is characterized in that the upper surface of the double seat bodies is provided with two coattail grooves in parallel; besides, each coattail groove is matched with the lower bottom coattail lug boss of the bottom lock of a container (caisson) used for navy; one end of the coattail groove is provided with a stop block. In the utility model, the combined double coattail grooves are adopted as the connection grooves with the bottom lock; besides, each coattail groove is matched with the lower bottom coattail lug boss of the bottom lock of the container (caisson) used for navy and the profile size of each coattail groove is small; therefore, the problem that the arrangement between the containers (caisson) used for navy needs to be compact can be solved; besides, the double coattail bases can be completely suitable for the connection and fixing between the bottom lock of container (caisson) used for navy and a board. Besides, the container (caisson) used for navy have the characteristics of compact structure, convenient use, and the like. The two ends of the double bases are provided with cuts, thus being capable of lightening the weight of the base bodies and increasing the welding area.