The development of fourth-generation reactors and advanced nuclear energy systems require high-precision, multi-nuclide, and wide-energy-area neutron nuclear data. However, the current nuclear energy-related nuclear fission data in the China Nuclear Data Evaluation Library (CENDL library) is incomplete and cannot meet the current needs. It is extremely important to establish reliable calculation methods and tools for the neutron nuclear data. Based on the Monte-Carlo method, this work established a model for the calculation of the pre-neutron fission fragment. The mass and kinetic energy distribution of 232Th(n,f) reaction at the medium- and low- incident neutron energies were studied. The calculation of the mass distribution with the different incident energies were compared with the experiment. The maximum deviation of this work from the experimental data is ~1%, which is advantageous compared with the GEF and TALYS code (maximum deviation from the experimental value is ~2%). The calculation of the pre-neutron fission fragment kinetic energy also shows a good agreement with experiment. The results indicate that this model can well describe and predict the characteristics of pre-neutron fission fragment for 232Th(n,f) reaction at the medium- and low- incident neutron energies. It also provides a new idea for the calculation of neutron-induced actinide fission reaction.