We report the calculations of vectorial nonlinear properties of rubidium vapor for 87Rb D2 transition at moderate intensities. The results are compared with self-rotation and diffraction experiments. Different from Kerr nonlinearity, optimal intensity exists here, which depends on beam geometry. For intensities close to the optimal, the vectorial mechanism is much more efficient than a scalar one, and strong self-action for wide beams can be obtained with it.