Abstract: Supercontinuum generation and self-focusing effect of ultra-short pulse propagation in Kerr media were investigated according to (3+1) dimensions' nonlinear Schrdinger equation. Results indicate that spectral super-broadening without self-focus can be achieved by adjusting the pump power and the beam diameter. The process of a small diameter ultra-high power pump beam propagating in BK7 glass with or without small scale modulation was simulated. The experimental results indicate that the near-field beam quality improves when the pump power decreases. In this case, the pump beam doesn't collapse by whole beam self-focus and other nonlinear effects are restrained. In order to keep pump intensity in propagating, the best input power used for supercontinuum generation is near the whole beam