Abstract: The RANS/NLAS coupling method is used to simulate and optimize the fluctuating pressure environment of a rocket fairing under transonic conditions. The results indicate that the RANS/NLAS method can accurately simulate the fluctuating pressure with less grids. When transonic flow passes the rocket fairing, shock waves/boundary layer interaction occurs at the shoulder, and a large separation region is formed at the inverted cone, thus the fluctuating pressure environment is severe on both the shoulder and the inverted cone. With the increase of the attack angle, the fluctuating pressure environment on the leeward side of the shoulder becomes severe, but that on the inverted cone region tends to be alleviated. To optimize the fluctuating pressure environment at the inverted cone, three new outline profiles of the inverted cone are designed, i.e. the straight line shape, the sinusoidal line shape and the “tangent arc + circular arc” shape, respectively. The time-averaged friction coefficient C_f, separation region, root-mean-square pressure coefficient C_{p_rms} of the three designs are compared, and the result shows that the “tangent arc + circular arc” design is the most effective in optimizing the fluctuating pressure environment.