All-inorganic perovskite has attracted significant attention due to its excellent nonlinear optical characteristics. Stable and low-toxic perovskite materials have great application prospects in optoelectronic devices. Here, we study the nonlinear optical properties of ${\mathrm{CsPbCl}}_x{\mathrm{Br}}_{3-x}$ ($x=1$, 1.5, 2) nanocrystals (NCs) glass by open-aperture Z-scan. It is found that the two- (2PA) and three-photon absorption (3PA) intensity can be adjusted by the treatment temperature and the ratio of halide anions. The perovskite NCs glass treated at a high temperature has better crystallinity, resulting in stronger nonlinear absorption performance. In addition, the value of the 2PA parameter of ${\mathrm{CsPbCl}}_{1.5}{\mathrm{Br}}_{1.5}$ NCs glasses decreases when the incident pump intensity increases, which is ascribed to the saturation of 2PA and population inversion. Finally, the research results show that the 2PA coefficient ($0.127\mathrm{cm}{\mathrm{GW}}^{-1}$) and 3PA coefficient ($1.21\times {10}^{-5}{\mathrm{cm}}^3{\mathrm{GW}}^{-2}$) of ${\mathrm{CsPbCl}}_1{\mathrm{Br}}_2$ NCs glass with high Br anion content are larger than those of ${\mathrm{CsPbCl}}_2{\mathrm{Br}}_1$ and ${\mathrm{CsPbCl}}_{1.5}{\mathrm{Br}}_{1.5}$ NCs glasses. This is mainly due to the greater influence of Br anions on the symmetry of the perovskite structure, which leads to the redistribution of delocalized electrons. The revealed adjustable nonlinear optical properties of perovskite NCs glass are essential for developing stable and high-performance nonlinear optical devices.