Abstract: Through pressure measurement in a wind tunnel, the wind pressure distribution, total forces and Strouhal numbers of rectangular tall buildings with different corner radius under various wind angles were investigated. The near wake characteristics of the rectangular tall buildings with and without rounded corners were observed by PIV experiment, through which the influence mechanism of rounded corners on the wind load characteristics of the buildings was revealed from the perspective of flow field. Results indicated that under critical wind angle, the separated shear layer reattaches on one side face to form a separation bubble. Therefore, the drag force attains a valley value, and the lift forces and Strouhal number reach peak values. Compared with the building without rounded corner, the critical wind angles of those with rounded corners are smaller. The parameters which control the Strouhal number are the transverse projected width and the distance between vortex pairs in the wake. For the rounded-corner buildings of specific rounded radius, the Strouhal number is increased within some wind angles. The drag force is closely related with vortex pairs in the wake. After adopting the rounded corner, the dimensions of the vortex pairs decrease, while the transverse velocity in the wake increases which implies the intense mixing motion of the fluid and weakened vortex pairs. It gives rise to the decreasing of drag forces. In addition, the irregularity and randomness of vortex shedding are enhanced, while its strength is attenuated by the rounded corner. Then the lift forces are caused to be decreased. However, this decrease tendency is not found for all wind angles.