Fabricated construction platform and construction method for underwater cofferdam

The invention belongs to the technical field of engineering construction equipment, and relates to an assembly type construction platform for an underwater cofferdam, the assembly type construction platform comprises a shaping steel platform and a sand filling mechanism, the sand filling mechanism comprises a fixed sand filling cross beam, a movable sand filling cross beam and a sliding rail, the fixed sand filling cross beam is fixedly arranged on the inner ring of the shaping steel platform, and the movable sand filling cross beam is fixedly arranged on the sliding rail. Sliding rails are arranged at the two ends of the inner ring of the shaping steel platform, a movable sand filling cross beam parallel to the fixed sand filling cross beam is installed on the sliding rails in a sliding mode, and the fixed sand filling cross beam and the movable sand filling cross beam are connected with sand filling pipes through sand filling pumps respectively. The invention further relates to an assembly type construction