Abstract: As a non-destructive assay technique, neutron detection technology is a better choice for monitoring the plutonium concentration of the uranium-plutonium solution system.A study on the neutron detection efficiency of uranium-plutonium solution system is carried out to monitor the plutonium concentration of the system, based on a typical cylindrical equipment containing uranium-plutonium solution and a typical thermal neutron detector. The effects of detector position, moderator and shield configuration, solution concentration and solution axial profile on the detection response were studied, and the optimized detection efficiency and the contribution of different axial sections to the detector response were obtained. The theoretical value of the neutron detection efficiency was verified by the measured value of the neutron count rate of the plutonium solution sample, and they were in good agreement. The study on neutron detection response of the uranium-plutonium solution system can be applied to the later monitoring of the plutonium concentration of the uranium-plutonium solution equipment, which provides a reference for the design of the technical monitoring scheme of the plutonium concentration of the equipment and lays a foundation for the subsequent study of the plutonium concentration monitoring algorithm.