After more than 10 years of development in recently, the aluminum alloy footbridges have gradually become a new branch of municipal engineering footbridges. In the existing engineering practices, the method of factory prefabrication and on-site assembling is mostly used for the construction of aluminum alloy footbridge superstructure. But the lower foundation is still used of the traditional drilling/digging piles or cast-in-place enlarged foundation, which leads to the long in-site construction period of the whole bridge, and is hard to fully play and reflect the advantages of the rapid construction of aluminum alloy footbridge. In order to solve this problem, combined with the characteristics of aluminum alloy footbridge, the main dimensions of the lower foundation are calculated according to the trussed aluminum alloy footbridges in two different spans. The corresponding rapid construction scheme of pile foundation and enlarged foundation is proposed, and the specific solutions for the key points in the construction scheme are put forward.