The differential equation ,discribing the small scale self focusing effects caused by nonlinear growth of perturbation when laser beams are propagating in nonlinear media with gain(or loss), have been deduced from nonlinear propagational equation. Some characteristics of small scale self focusing of laser beams propagating in nonlinear media with gain have been analysed. Variations of cutoff spatial frequency, the fastest growing frequency, integral exponential gain of perturbation with different parameters have been specified.