Abstract: The photochemistry of 6’-nitro-1, 3, 3-trimethylindolinobenzopyrylospiran, Ⅰ, and 6’-nitro-1-phenyl-3, 3-dimethylindolinobenzopyrylospiran, Ⅱ, was investigated.Both direct and sensitized photolyses of I afforded the coloured species, the merocyanine, Ⅲ, with quantum yields of 0.42 and 0.32, respectively.Direct irradiation of Ⅱ gave the corresponding merocyanine, Ⅳ, with quantum yield of 0.40, while the quantum efficiency on xanthone sensitization of Ⅱ was determined as 0.58 for the same photoproduct.Undoubtelly, both singlet and triplet were involved in the photocolouration of the spi-ropyrans.These results and the bracketing relationships signified that a considerable fraction of Ⅲ came directly from the excited singlet occured on the direct photolysis of Ⅰ, but 70% of Ⅳ was originated from the excited triplet on the direct photolysis of Ⅱ.The triplet parameters were obtained from the sensitization of biacetyl phosphorescence by Ⅰor Ⅱ at varying biacetyl concentrations.These were:φ_Ⅰ^ISC＝0.11,φ_Ⅱ^ISC＝0.48;³K_Ⅰ^dt＝3×10⁴S^-1,³K_Ⅱ^dt＝9×10⁴S^-1;³K_Ⅰ^r＝0.12×10⁴S^-1,³K_Ⅱ^r＝2.52×10⁴S^-1 Thus, the lower magnitute of ³φ_r^Ⅰ was shown to derive from lower intersystem-crossing quantum yield of Ⅰ and the variation of the triplet life time of Ⅰ and Ⅱ with structure was relatively small.Finally, the electronic energy curves of styrene, a model compound, for twisting of the ethylenie bond were employed to assign that the zwitterion came from the excited singlet had a spiro configuratio and the zwitterion originated from excited triplet had a planar configuration.