The third-order nonlinear optical properties of a new subphthalocyanine complexe (bromo［tri-α-(2,4-dimethyl-3-pentyloxy) subphthalocyanine］ boron) was studied by Z-scan using 8ns laser pulses at 532nm. It was found that the compound shows a strong reverse saturation absorption (β=3.7×10-10 m/W) and nonlinear self-focusing refraction effects (n2=7.2×10-11 esu). The third-order nonlinear susceptibility (χ(3)) is 1.1×10-11esu.The effects of cone-chaped molecular structure and axially heavy-atom (Br) substitution on third-order nonlinear optical properties are also discussed.