The invention discloses a foundation pit lock pile water stop construction method, and relates to the technical field of lock pile construction. The foundation pit lock pile water stop construction method specifically comprises the following steps that firstly, the position where a lock pile needs to be built is detected, various data of the position are measured, and according to the data and theexisting standard, the lock pile is poured; and the strength of the lock pile is improved. According to the foundation pit lock pile water stop construction method, the surrounding of the position where the lock pile needs to be built is subjected to exploration detection, when the lock pile is poured, and after the lock pile is poured, effective and portable water stop can be carried out, the water stop effect is high, the phenomenon that due to involvement of water, the poured lock pile cannot be used is greatly avoided, a worker can more conveniently work, meanwhile, fewer faults appear inthe engineering, use cost is reduced, use by a user is facilitated, and the problems that at present, an existing foundation pit lock pile waterstop construction method is complex and poor in practicability are solved.