The invention relates to a secondary locking and temporary fixation structure for a main pier of a cross-river bridge. The secondary locking and temporary fixation structure mainly comprises steel pipe columns, steel pipe column connecting ends, anchor cables, deformed steel bars, brackets, temporary supports and an adjustable template supporting system. The steel pipe columns are arranged on a bearing platform and anchored to the steel pipe column connecting ends embedded in the bearing platform. The anchor cables and the deformed steel bars are arranged in the steel pipe columns, the lower ends of the anchor cables and the lower ends of the deformed steel bars are anchored to connecting end plates in the steel pipe column connecting ends, and the upper ends of the anchor cables and the upper ends of the deformed steel bars are anchored to a cast-in-place box beam bottom plate. The temporary supports are installed on the top of the pier, and the embedded deformed steel bars are arranged in the temporary supports. The brackets are arranged on corbels of the steel pipe columns and provided with a supporting seat, a bottom die is installed on the top face of the supporting seat, the installation angle of an integrated flank template is adjusted through adjustable stay bars, and the integrated flank template is fixedly connected with the bottom die. A core die is supported through an adjustable cross-shaped inner support. A secondary anchoring system is adopted in the structure, and the problem of uneven stress in the 0# block construction process is successfully solved. The invention further provides a construction method of the secondary locking and temporary fixation structure for the main pier of the cross-river bridge.