The load-displacement characteristic curves of C-series disc spring with outside diameter of 28 mm under different working conditions were obtained by static loading test with microcomputer controlled electronic testing machine. Based on the ABAQUS finite element software, the finite element model of disc spring was established and the numerical simulation was carried out under different displacement loads. The numerical models were tested and modified using the experimental data. The modified model agreed well with the measured results. On this basis, the finite element model of non-standard grooved disc spring was established, and the load-displacement characteristic curve and stiffness-displacement curve of the disc spring under different slot positions and different slots were calculated. The effects of different slotting positions and slotting modes on the disc spring load variation range, stiffness change rate, stiffness variation range, negative stiffness zone size and maximum equivalent stress were analyzed. This study has a certain reference value for the design of non-standard grooved disc spring and the application of negative stiffness element on the vibration isolation device.