Negative stiffness element (NSE) has extensive uses in engineering applications, such as vibration isolation,
energy harvesting, and mechanical metamaterial. However, to realize a linear negative stiffness characteristic is
still a challenging task. In this paper, we present a compact magnetic negative stiffness element (MNSE) that
composed of three rectangular permanent magnets and configured as repelling configuration in horizontal to
realize linear negative stiffness characteristic. The effects of the MNSE configuration parameters on the negative
stiffness characteristic are analyzed in detail. The results demonstrate that the magnitude of the negative
stiffness characteristic can be adjusted by changing the height ratio and width ratio between the central and
outer magnets. The height difference between the central and outer magnets can be used to tune the degree of
nonlinearity of the negative stiffness characteristic and to get the uniformity stiffness characteristic in the equilibrium
position. The procedure to realize the linear negative stiffness characteristic with the expected magnitude
and displacement range is developed and confirmed. The proposed MNSE and the design procedure offer
an engineering application foundation for the magnetic linear negative stiffness.