The invention relates to the technical field of graphite heat exchangers, in particular to a negative pressure type graphite heat exchanger detection method. The leakage point detection device includes a sealing device, a detection head, an industrial control computer, and plugs; during leakage point detection, the sealing device is arranged on one side of the heat exchanger, the detection head isinserted into a heat exchanging pipe at the other side of the heat exchanger, the detection head is connected to the industrial control computer; vacuum pressure maintaining test can be performed onthe heat exchange pipes one by one so as to determine the state of the heat exchange pipe according to the condition of pressure rising, and a broken heat exchanging pipe can be quickly found; a firstsealing plug and a second sealing plug are arranged on two ends of the broken heat exchanging pipe; the first sealing plug and the second sealing plug are connected through a connection rope, and inthis way, the problem that the broken heat exchanging pipe is difficult to find during maintenance of the graphite heat exchanger can be solved; the manner of using the plugs to seal the two ends of the broken heat exchanging pipe can avoid huge cost due to change of a single heat exchanging pipe, and the objective that the maintenance cost is saved by sacrificing a part of the heat exchanging efficiency.