Liquid scintillation detectors based on the time-of-flight method are important for neutron/gamma diagnosis in fusion ignition research, with rapidly decaying scintillators at the core. To meet the testing requirements for scintillator decay characteristics, this study developed a testing system based on the advanced time-correlated single photon counting principle and optimized the attenuation mechanism on the basis of a “filter + porous grating” structure for single photon acquisition. The system response time was found to be 0.84 ns, with dynamic range of light intensity measurement of 10⁴ and measurement accuracy of 0.61 ns. Notably, more than 95% of the signal can be attributed to single photons. Validation tests were conducted on BC501 and CLYC scintillators, which differ considerably in terms of decay characteristics, and the resultant decay curves for both scintillators were obtained. The decay constants of the BC501 scintillator were found to be 3.7 and 35.5 ns, which differ from the reference values by 0.5 and 3.2 ns, respectively. Similarly, the decay constants of the CLYC scintillator were found to be 1.4, 58.9, and 1 074 ns, which differ from the reference values by 0.4, 8.9, and 74 ns, respectively. These results confirm the reliability of the developed measurement system and will be applied in subsequent testing and comparison of scintillator samples.