Abstract: As the main type of fast reactor in the future development of nuclear energy, neutron calculation is very important for core design and safety analysis. The fast spectrum critical experimental facility is mainly used for the study of fast spectrum core design, core neutron behavior and nuclear data acquisition. At present, there is some progress in the research of fast spectrum critical experimental facility at home and abroad, but there is little research on the exact neutron simulation of fast spectrum critical experimental facility with square component plate fuel. The fast spectrum and few group cross section calculation software TULIP and the few group transport calculation software LAVENDER were developed by the Nuclear Engineering Computational Physics Laboratory of Xi'an Jiaotong University and integrated into LoongSARAX. LoongSARAX can be used to study its square assembly plate fuel fast spectrum critical experimental facility. LoongSARAX is a neutronics calculation program system developed by Xi'an Jiaotong University for liquid metal fast reactors. Based on the benchmark of the SNEAK fast spectrum criticality experimental facility, the modeling calculation analysis and preliminary verification of LoongSARAX were carried out. Firstly, based on the Monte Carlo program OpenMC, the homogenization modeling method of the critical experimental facility with plate fuel was analyzed, and the simplified model suitable for LoongSARAX was determined. Based on the two-step method system of TULIP and LAVENDER in LoongSARAX, the calculation model of the SNEAK criticality experimental facility was established, and the effective multiplication factor of the whole reactor, the reactivity coefficient of the core, the power distribution and the micro-section were analyzed, and the results were compared with OpenMC conducted a comparative analysis. The analysis shows that the calculation results of LoongSARAX for the plate fuel criticality experimental facility are in good agreement with the MC method calculation results in terms of effective proliferation factor and power distribution. Due to the complex structure of the MZA fuel assembly, the maximum deviation of the effective breeder factor after processing is greater than that after SNEAK fuel assembly processing. When the spatial weighted mixing of the axial plate fuel square component is carried out, smaller errors will be introduced for the component with high repeatability and weak non-uniformity, while larger errors will be introduced for the component with strong heterogeneity. The maximum deviation of the calculation results of safety rod and control rod value and the maximum deviation of the calculation results of typical component reactivity are small. At the same time, the calculation results of core power distribution show that the maximum error is within the reasonable range. LoongSARAX is suitable for the plate fuel criticality experimental facility and has the ability to calculate for the plate fuel criticality experimental facility. In addition, LoongSARAX has higher computational efficiency than MC software OpenMC in terms of computation time.