The utility model discloses a fuel cell bipolar plate water cavity sealing performance detection device which comprises an air source, a pressure stabilizing valve, a pressure gauge, an anode cavity valve, a cathode cavity valve, a press rotating handle, a press upper die, a water cavity valve, a test upper end plate, a first membrane electrode, a tested polar plate, a second membrane electrode, avoltmeter, a test lower end plate and a press lower die. During detection, the anode cavity valve, the cathode cavity valve and the water cavity valve are closed, the valve of the pressure stabilizing valve is opened, the pressure range is adjusted to be 0.05-0.2 MPa, after the reading of the voltmeter is stable, the reading of the voltmeter is observed, and if the absolute value of the voltage is higher than 0.1 V, it is considered that leakage exists. According to the utility model, a voltage signal is used as a judgment indication of airtightness, the sensitivity is high, the detection speed is high, the signal is easy to acquire, automatic operation is realized, and the production detection efficiency is improved.