Broadband laser can be used to relax restriction of nonlinear effect and obviously improve output power of high-power solid laser systems, because of the spectral bandwidth of such kind of broadband laser can delay the onset of self-focusing. It is found that the degree of self-focusing suppression is closely related to the ratio of bandwidth and pulse duration, in the same pulse duration the bigger bandwidth is, the more obvious restraint effect is, and in the same bandwidth the restraint effect of bandwidth will become weaker with increasing the pulse duration. In actual neodymium-glass laser amplifying system, limited bandwidth can propagate through the amplification system due to the limited gain bandwidth and the gain narrow, which indicates clearly that the pulse duration as short as picoseconds is needed in this kind of solid laser system to achieve restrained small-scale self-focusing effect, while for longer pulse such as tens of picoseconds even nanoseconds, such limited bandwidth almost cannot influence the evolution of self-focusing.