Abstract: Environmental micro-vibration is a critical factor affecting the performance of semiconductor manufacturing and measurement equipment, and its control has become a complex and challenging issue in the field of modern precision engineering. Air springs are widely used in micro-vibration isolation due to their adjustable natural frequency and excellent low-frequency vibration isolation performance, but their load-bearing capacity is limited. In contrast, metal coil springs have high load-bearing capacity but relatively poor vibration isolation performance. To address this, we develop a novel metal-air combined spring isolator to integrate the high load-bearing capacity of metal coil springs with the high vibration isolation efficiency of air springs. Based on the ANSYS Mechanical/Fluent finite element software, this study employs a fluid-structure interaction method to calculate the vertical static and dynamic stiffnesses of the combined spring. Additionally, the influence of initial air pressure and the structural parameters of the metal coil spring (wire diameter, mean diameter, and number of active coils) on its performance is analyzed. Furthermore, parameter sensitivity analysis and error evaluation are conducted to quantify the impact of each parameter on vibration isolation efficiency under environmental micro-vibration. The validity of the established model is verified by comparing simulation with experimental results. The research indicates that the initial air pressure and the wire diameter of the metal coil spring have a significant influence on the vertical static stiffness of the combined spring, while the influence of the mean diameter and the number of active coils of the metal coil spring is relatively minor. In the parameter sensitivity analyses under environmental micro-vibration, the parameters are ranked in descending order of influence as follows: initial air pressure, wire diameter, mean diameter, and number of active coils. In terms of vibration isolation performance, when combined springs with wire diameters of 4 mm and 5 mm are respectively used, the isolation vibration level can meet the VC-C standard. In contrast, when an air spring is used alone, its vibration isolation performance can only meet the VC-D standard.