Natural supercavitations in water and drag-reducing solution, respectively, were numerically simulated based on unsteady Reynolds averaged Navier-Stokes scheme, with application of mixture-multiphase model. The Cross viscosity equation was adopted to represent the fluid property of aqueous solution of turbulent drag-reducing additives. The configuration and resistance characteristics of natural supercavitation were discussed respectively. The numerical simulation results indicated that at the same cavitation number, the length of supercavity in drag-reducing solution is larger than that in water, and the drag coefficient is smaller than that in water. The surface tension plays an important part in cavity generation and maintaining. Furthermore, the numerical simulation results are in good agreement with the available experiments.