Magnetic particle imaging is a new type of tracer imaging technology that uses the nonlinear magnetization characteristics of magnetic particles in magnetic field-free to image the measured objects. The spatial resolution is determined by the fineness of magnetic field-free, and the fineness is determined by the spatial magnetic field gradient. To improve spatial resolution, the static magnetic field structure which can produce large magnetic field gradient is combined with the driving structure to form a magnetic field-free line system. Firstly, this article designs static magnetic field structure based on ring magnet array. The large gradient static magnetic field is used to construct fine magnetic field-free line. Secondly, the driving structure is designed, which is based on Helmholtz coil and its driving method. The relationship between magnetic field-free line scanning range and driving current is determined. Finally, the spatial resolution of the magnetic field-free line system is calculated and its regularity with the magnetic field gradient and particle sizes is studied. Experimental results show the magnetic field gradient generated by the static magnetic field structure based on ring magnet array is 4. 804 T/ m, and the spatial resolution is 0. 540 mm when the 30 nm magnetic particle is used. The magnetic field-free line can scan within 30 mm range. It proves the feasibility of magnetic field-free line system based on ring magnet array for high-resolution magnetic particle imaging.