Construction method of lock catch steel pipe pile cofferdam suitable for thin covering layer hard riverbed

The invention discloses a construction method of a lock catch steel pipe pile cofferdam suitable for a thin covering layer hard riverbed. The construction method comprises the following steps that guiding is carried out on a steel platform by using a positioning guide plate, holes are guided by using a steel sleeve, lock catch steel pipe piles are inserted after the holes are guided, the adjacent lock catch steel pipe piles are connected through lock catches, and then soft consolidation treatment is carried out on the lock catch steel pipe piles, groove sealing concrete is poured on the inner side of the lock catch steel pipe piles, groove sealing medium-coarse sand is backfilled on the outer side of the lock catch steel pipe piles, a triangular bracket, an enclosing purlin and an inner support are installed, concrete is poured for sealing the bottom after foundation cleaning, a bearing platform and a pier body are constructed in a cofferdam, then medium-coarse sand is backfilled between the lock catch steel