Abstract: For the quantitative analysis of the focusing effect of superconducting flux focuser (SFF) for direct current superconducting quantum interference device (DC SQUID), "magnetic field, no current" module of COMSOL is used to conduct the electromagnetic simulation. We systematically investigate the impact of geometric parameters of SFF on magnetic field amplification G. The results indicate that G is maximized when the square aperture is centered. Moreover, G is proportional to the ratio of the concentrator's side length to the square aperture's side length and to the thickness of the superconducting film, while inversely proportional to the slit width. In practical applications, a batch of superconducting flux focusers were designed and fabricated to enhance the magnetic field detection capability of high-temperature superconducting DC SQUID magnetometers, effectively increasing the active area by a factor of 2.28 compared to the original, with white noise as low as 50 fT·Hz^−0.5. Accounting for assembly errors caused by packaging, the simulation results match the experimental data well. This simulation analysis method can provide theoretical guidance and design basis for the development of high-performance high-temperature superconducting magnetic sensors.