Abstract: Liquid scintillation detector based neutron multiplicity counting device for nuclear material accountancy in nuclear safeguards was optimal designed and established, and some related performance tests were also carried out in this work, which indicates the operating state of this device is stable and all the indications are acceptable. Meanwhile, some related researches for neutron multiplicity counting have been done, which included the simulated measurements in the laboratory for ²⁵²Cf source and plutonium standards. The experimental results show that the detection efficiency of this device is better than 15%, and the relative standard deviation of measurements is 8.6%. It proves that this new neutron multiplicity counting device has capability to take place of ³He detector based neutron multiplicity counting device by long-time signal collection in allowed condition, and accomplish the quantification tasks for nuclear material accountancy in nuclear safeguards by neutron multiplicity analysis.