In general, the aerodynamic stability of long span bridges is evaluated based on the results of wind tunnel tests in the low Reynolds number region, because in almost all wind tunnel tests, it is impracticable to satisfy Reynolds number similitude. Therefore, in order to correctly evaluate conventional wind tunnel test results, Reynolds number eﬀects on the aerodynamic force coeﬃcients acting on bridge decks must be carefully investigated. This paper investigate the Reynolds number effect on the aerodynamics of bridge deck section measured in the wide Reynolds number region from to based on the dimension of deck height in smooth flow. For the simulation of fluid flow, open-circuit and blowing wind tunnel was used for which the maximum nominal turbulence was 0.1%. The results show that increasing Reynolds number has less effect on the drag coefficient and Strouhal number and parameters in downstream of the model. In other words, variation of drag coefficient and Strouhal number is very small in Reynolds numbers over 20000. Increasing Reynolds number would not be followed with an outstanding change at value of velocity defect but causes to reduce half width, of course, it has no effect in rate growth of half width.