The invention discloses a construction process for an underwater churning-driven cast-in-place bored pile by adopting a chemical slurry powder to make slurry and protect a wall, comprising the following specific operation steps of: 1, making construction preparation, specifically, fully preparing equipment, tools and objects required by construction, flattening and compacting a construction site,cleaning impurities, removing soft soil, measuring and labeling the center of a pile position, and embedding a pile casing; 2, putting a drilling machine in place, moving the drilling machine to the pile casing, conducting installation and adjusting on the drilling machine, making a drill bit to be aligned with the center of the pile position, integrally checking the drilling machine, and removingfaults in time; and 3, conducting wall protection by slurry, specifically, arranging a slurry pool in a construction site. A double-bottom sand bailing drill is used for bailing slag, and through combination with a pump suction reverse circulation hole-cleaning construction process, the hole cleaning speed is high, hole bottom sediment can be effectively controlled, chemical slurry is prepared according to a proportion determined based on the construction site geology and actual conditions, complex geological conditions in water are considered, the wall protecting capacity of the slurry is improved, the hole forming quality is guaranteed, and the construction progress is accelerated.