Slender structures with square cross-section, which are widely used in civil engineering, expose in the oblique wind during its service. The wind loads on this structure can be simplified as the aerodynamic forces on a yawed square cylinder. Unlike cylinders under wind normal to its length, an estimation of aerodynamic forces for yawed square cylinders are still unclear. In the present study, the wind pressure distribution on the yawed cylinder is tested in the wind tunnel to illustrate the effects of the skew angels on aerodynamic characteristics. The results show that the conventional wind velocity decomposition can only estimate the pressure distribution before the separation points rather than estimate the whole aerodynamic forces on the yawed cylinders. The mean value and standard deviation of aerodynamic forces on the yawed cylinder are smaller than those on the normal cylinders due to the weak wind pressure on the leeward side. The yawed cylinders also have smaller vortex shedding frequency, weaker vortex and wider frequency band than the normal cylinders. Therefore, it is conservative wind load, which uses mean aerodynamic forces for the normal cylinder instead of the yawed cylinder, but the change of the vortex shedding frequency and band of frequency may induce the significant difference on wind-induced vibrations.