Based on spatiotemporal nonlinear Schrödinger equation, we numerically study the modulation instability how to affect
the self-focusing of broadband pulsed-beam with large chirp. We found that the chirp of the pulse can postpone the
speed of the modulation growth from the simulation results. However, it is not work all along with increasing chirp value,
but tend to a certain value. The curves of the contrast of chirped pulsed-beam will become superposition as chirp value is
enough large when it propagates in nonlinear medium. Then, the influence of pulse bandwidth on modulation will
become small, when the chirp has enough value in anomalous dispersion medium. At last, we also found that, in
anomalous dispersion medium, temporal modulation growth and small-scale self-focusing can occur before the whole
self-focusing, furthermore, the temporal instability will lead spatial focusing and splitting to bring forward.