An analytical model is developed for modeling aerodynamic flutter derivatives for long-span Open-Truss Girder Suspension Bridges and their interaction. The approach suggested here is to synthesize the wind derivatives based on proposed functions interpolated from experimental results of previous studies. The model solves the equation of motion and the synthesized aerodynamic forces are solved to find the critical wind velocity of the suspension bridge. The solution procedure and assumptions of the approach are verified using the Golden Gate Bridge flutter analyses, where the experimental aerodynamic coefficients of the bridge are modeled as a function of the wind velocities in the proposed procedure and compared with the analysis based on the interpolated coefficients. The results agree with the results in the literature. The result of the proposed analytical model is close to the values extracted from previous researches.