Nowadays, the sustained technological progress in high-intensity lasers is opening up the possibility of super-intense laser pulses to trigger or substantially influence nuclear reactions. However, it is a big challenge to quantitatively measure the reaction products because of the interference of electromagnetic pulses induced by high-intensity lasers. Fast scintillation detectors are widely chosen for fast neutron detection. The calibration of neutron detectors is crucial to measuring the yield of neutron products. Since one large signal superimposed by a number of neutron signals appears during a short period, it is difficult to directly and precisely calibrate the detectors' response for a single neutron. In the present work, we developed a direct calibration method with a gated fission neutron source 252Cf to solve this problem. This work demonstrates that the gated fission neutron source approach, with a unique "Pulse Shape Discrimination & Time of Flight window" function, has the highest background-γ-rejection and improves the confidence level of the final results for both liquid and plastic scintillator. Compared with the result of Compton edge method and neutron beam method, the gated fission neutron source method achieves much cleaner neutron signals and avoids interference caused by the modeling accuracy of the neutron detectors. This approach can be widely used in laser-driven nuclear physics experiments with higher accuracy for neutron detection.