Abstract: Reynolds number effects on Strouhal number are very important in the study on Reynolds number of bridge decks. The method to obtain aerodynamic forces by spatial integration of the surface pressures is used. With it both the mean values of net aerodynamic forces and their time histories can be obtained. The RMS value and the frequency of aerodynamic forces can then be evaluated. The Strouhal numbers of the stationary section are calculated from the peak frequency of the net aerodynamic forces, and the Reynolds number effects on Strouhal number are investigated. A wide range of 2.7×10⁴ to 1.4×10⁶ based on the deck heights are investigated, in which the larger one is only one magnitude less than the full-scale. It is found that the Strouhal number of flat-box girder bridge deck is affected by Reynolds number effects, and the Reynolds number in the transition region is from 2×10⁵ to 4×10⁵.