A flange catcher is an n-shaped body, and the upper end of the n-shaped body is connected with a lifting lug. Two columns with different lengths of the n-shaped body are steel columns, the lifting lug is vertically connected onto a steel plate surface of the n-shaped body, and a hole is arranged on the lifting lug. The catcher can also be an L-shaped body, and a hole is arranged on the L-shaped catcher. The L-shaped body mainly comprises a steel plate, and a short column of the L-shaped body is a steel column. During connection of an oil pipeline under the ocean, a flange of the oil pipeline under the ocean is stably located on the flange catcher, a diver conveniently guides an engineering ship crane underwater to hoist and butt the oil pipeline under the ocean, a flange face of the oil pipeline under the ocean is effectively protected from damage, operation time is saved, and working efficiency is improved. Besides, underwater working time is shortened for the diver, and safety factor of underwater operation and integral construction safety are improved for the diver.