The high static stiffness and low dynamic stiffness characteristics of the quasi-zero-stiffness isolator effectively address the conflict between low stiffness and high load-bearing capacity in traditional isolators. However, most existing quasi-zero-stiffness isolators are designed for small load conditions and have a less compact structure, making them difficult to apply in situations with higher loads and limited installation space. In view of this, a high-load compact quasi-zero-stiffness isolator is proposed and its heavy-load low-frequency vibration isolation characteristics is verified through experiments. The isolator utilizes coaxial permanent magnet rings to provide negative stiffness and achieves quasi-zero stiffness by paralleling with circumferentially distributed coil springs. The restoring force expression of the coaxial permanent magnet rings is derived using the equivalent magnetic charge method, and finite element simulation of the permanent magnet rings is conducted using COMSOL software to verify the accuracy of the analytical expression. Subsequently, a nonlinear dynamic theoretical model of the vibration isolation system is established, and the equations are solved using the harmonic balance method. The theoretical results are also verified using the Runge-Kutta method. Additionally, the influence of system damping ratio and external excitation amplitude on the system’s amplitude-frequency response and force transmissibility is discussed. Finally, a prototype of the isolator is fabricated, and quasi-static static tests and sinusoidal excitation tests are conducted. The results indicate that the coaxial magnet ring quasi-zero-stiffness isolator can achieve compact heavy-load low-frequency vibration isolation with an installation height of 60 mm and a load capacity of 160 kg. When the controlled excitation force amplitude is 20 N,the initial vibration isolation frequency is as low as 3.6 Hz, with a vibration isolation efficiency of 44.3% (5 dB) at 5 Hz and 90% (20 dB) at 10 Hz.