Abstract: According to the application requirements of long-life cores, research on improving the core life of small pressurized water reactor (PWR) was carried out. Taking rod-shaped fuel as the object, the selection of different lattice sizes and different burnable poisons was calculated, and the influencing factors of core life of small PWR were obtained. By carrying out transport-burnup calculations on fuel lattices of different sizes, the burnup optimum lattice size was obtained. The components were built with the burnup optimum lattice size and the actinide nuclide ²⁴⁰PuO₂ with good conversion performance was selected as a burnable poison. Using the characteristic of ²⁴⁰Pu absorbing neutrons converted to fissile nuclide ²⁴¹Pu, reactivity control of the core and life extension are achieved. Through the reasonable selection of fuel lattice size and burnable poison, the fuel utilization ratio is improved and the core life is extended.