Abstract: On the basis of the vector non-paraxial nonlinear Schrdinger equation, the property of self-focusing of intense laser beam is analytically investigated by a modulation theory. The role in self-focusing of the nonzero ▽·E term and that of nonparaxiality are compared. It is shown that both effects can arrest catastrophic collapse of the beam, leading to a periodic focusing-defocusing oscillation. For the aspect of collapse arresting, the nonzero ▽·E term is dominant over nonparaxiality.