The invention relates to a tester for testing the pipeline volume through a differential pressure method. The tester comprises a workbench and a control circuit. The control circuit is arranged on the back of the workbench. The workbench is equipped with a constant-pressure gas storage tank, a pressure maintaining vessel, a fixed station and a water detection device, wherein an inlet of the constant-pressure gas storage tank is externally connected with a gas feed port through a capillary tube, an outlet of the constant-pressure gas storage tank is communicated with the pressure maintaining vessel, a differential pressure meter is arranged in the pressure maintaining vessel, an inlet of the differential pressure meter is communicated with the pressure maintaining vessel, an outlet of the pressure maintaining vessel is communicated with an inlet of the fixed station, an outlet of the fixed station is communicated with an inlet of the water detection device, a test sample is placed on the fixed station, the devices are communicated through the capillary tube, and the devices are electrically connected with the control circuit on the back so as to be controlled in an unified mode. Product leakage is detected according to the working principles of a water detection method and an enclosed volume manometric method, and qualitative leakage detection can be quickly carried out and the amount of leakage can be quickly and quantitatively determined without the need to put a product in the water.