Abstract: Square cross-section is commonly used in high-rise structures in civil engineering. The vortex-induced vibration (VIV) is one of significant factors which threaten the safety of these structures. A rigid section square cylinder model is used in a series of pressure test in a wind tunnel to study the variation of aerodynamic forces and vortex shedding frequencies with the angle of attacks. The critical wind speed of VIV also is estimated. The results show that the angle of attack have a significant effect on aerodynamic forces and vortex shedding frequency on which the critical wind speed of VIV depends. As for the square cylinder, the lowest critical wind speed of VIV occurs when the angle between wind and the windward face of the model is around 74.