Abstract: Objectives To design a novel adjustable magnetic constant-force quasi-zero stiffness structure with magnetic constant-force characteristics, capable of generating quasi-zero stiffness over an ultra-long stroke range. Methods Firstly, a finite element model of the magnetic constant-force quasi-zero stiffness structure was established using ANSYS Maxwell 2024 electromagnetic field low-frequency simulation software. Secondly, to enhance the magnetic constant-force uniformity, parametric scanning was employed to reveal the influence of structural parameters on force uniformity, and optimal geometric dimensions were determined. Subsequently,theoretical analyses of axial magnetic force and torque around the z-axis for the constant-force structure were conducted. Results The results show that the designed structure can adjust the constant-force magnitude between ±683.19 N by rotating the outer permanent magnet, and generate stable magnetic constant-force over a 40 mm ultra-long stroke range with a relative force standard deviation of 4.34%, demonstrating excellent force uniformity. Conclusions This design provides a new approach for the development of quasi-zero stiffness vibration isolators.