The power generation of single-axis PV trackers system is significantly higher than that of the fixed photovoltaic system， making them widely used in recent years. The single-axis PV tracker is prone to torsional aerodynamic instability in the strong wind condition due to its low torsional stiffness， resulting in structural damage. In order to understand the occurrence conditions and mechanism of this vibration further， the present study investigates the influence of structural natural frequency， tilt angle， damping ratio and other parameters on torsional aerodynamic instability through wind tunnel tests with elastic support. The variations of aerodynamic damping and aerodynamic stiffness with wind speed and tilt angle are focused. The result shows torsional aerodynamic instability of single-axis PV trackers shows strong aerodynamic coupling effect. The aerodynamic damping and aerodynamic stiff? ness are significant parameters that can influence aerodynamic instability， which are sensitive to wind speed and tilt angle with selfexcited vibration characteristics. The increase in torsional stiffness can effectively limit the amplitude at certain tilt angles and im ? prove the critical wind speed of the structure at various tilt angles. The unstable tilt angle is approximately located in the range of -15°~20°. It is suggested that a large tilt angle can be used to avoid aerodynamic instability in strong wind. When a small tilt an? gle is inevitable， higher critical wind speed corresponds to a 0° tilt angle.