Heat exchanger test system and test method

The invention relates to the technical field of ultralow temperature testing, in particular to a heat exchanger testing system and method, and the system is characterized in that a testing box is provided with a cavity for placing a heat exchanger; the liquid nitrogen tank is connected with the test box; the inert gas pressurizing device is connected with the test box and is suitable for filling inert gas into the test box until a detection pressure value is reached after the temperature in the test box reaches a preset value; the heat exchanger test method comprises the following steps: putting a pretreated heat exchanger into a test box, filling liquid nitrogen into the test box until the temperature reaches a preset value, and then filling inert gas into the test box until the temperature reaches a detection pressure value; the controllable temperature of liquid nitrogen ranges from minus 180 DEG C to minus 45 DEG C, and it is ensured that an ultralow-temperature environment needed by heat exchanger testin