A high-resolution neutronics model for the production of plutonium-238 (²³⁸Pu) in high-flux reactors is proposed and compared using three methods: filter burnup, single energy burnup, and burnup extremum analysis. The first two methods achieve high spectrum resolution (up to 1 eV) and construct importance and yield curves for the full energy range. The third method combines these curves to consider the effect of irradiation time on production efficiency, constructing extreme curves. These curves, which quantify the transmutation rate of nuclei in each energy region, are physically meaningful due to their similar distributions. A high-resolution neutronics model for ²³⁸Pu production is established based on these curves, demonstrating its universality and feasibility. The model guides neutron spectrum optimization, improving ²³⁸Pu yield by up to 18.81%. It reveals the law of nuclear transmutation across all energy regions with high spectrum resolution, providing theoretical support for high-flux reactor design and ²³⁸Pu irradiation production. ²³⁸Pu is a radioactive isotope with a half-life of 87.7 years, used as a heat source in radioisotope thermoelectric generators (RTGs) and radioisotope heater units. High-flux reactors provide stable neutron flux for ²³⁸Pu production. Two methods are used: irradiation of americium-241 (²⁴¹Am) or neptunium-237 (²³⁷Np). The latter method is more common due to its high purity and low radioactivity. However, the production process lacks a precise neutronics model, leading to low transmutation rates and high costs. The study analyzes the production process, highlighting the need for neutron spectrum optimization to improve efficiency and reduce costs. Previous studies have proposed various methods for neutronics modeling, but none have considered the complete nuclear chain during irradiation. The proposed model provides a high-resolution approach for neutron spectrum analysis and optimization in ²³⁸Pu production.A high-resolution neutronics model for the production of plutonium-238 (²³⁸Pu) in high-flux reactors is proposed and compared using three methods: filter burnup, single energy burnup, and burnup extremum analysis. The first two methods achieve high spectrum resolution (up to 1 eV) and construct importance and yield curves for the full energy range. The third method combines these curves to consider the effect of irradiation time on production efficiency, constructing extreme curves. These curves, which quantify the transmutation rate of nuclei in each energy region, are physically meaningful due to their similar distributions. A high-resolution neutronics model for ²³⁸Pu production is established based on these curves, demonstrating its universality and feasibility. The model guides neutron spectrum optimization, improving ²³⁸Pu yield by up to 18.81%. It reveals the law of nuclear transmutation across all energy regions with high spectrum resolution, providing theoretical support for high-flux reactor design and ²³⁸Pu irradiation production. ²³⁸Pu is a radioactive isotope with a half-life of 87.7 years, used as a heat source in radioisotope thermoelectric generators (RTGs) and radioisotope heater units. High-flux reactors provide stable neutron flux for ²³⁸Pu production. Two methods are used: irradiation of americium-241 (²⁴¹Am) or neptunium-237 (²³⁷Np). The latter method is more common due to its high purity and low radioactivity. However, the production process lacks a precise neutronics model, leading to low transmutation rates and high costs. The study analyzes the production process, highlighting the need for neutron spectrum optimization to improve efficiency and reduce costs. Previous studies have proposed various methods for neutronics modeling, but none have considered the complete nuclear chain during irradiation. The proposed model provides a high-resolution approach for neutron spectrum analysis and optimization in ²³⁸Pu production.