The photochromic properties and reaction mechanism of title compounds have been examined with steady method on compounds 3-phenyl-3-[3-methylbenzothiophene-2-yl]-3H-naphtho[2,1-b]pyran (1) and 3-phenyl-3-[benzofuran-2-yl]-3H-naphtho[2,1-b]pyran (2) and nanosecond laser flash photolysis techniques on compound 3-phenyl-3-[1,2-dimethylindol-3-yl]-3H-naphtho[2,1-b]pyran (3). The influence of oxygen on transient spectra and decay kinetics of compound 3 has been investigated. Both excited singlet state and triplet state are involved in the photochromic mechanism of compound 3. The influence of molecular structure on photochromic behavior has been studied also. Decay kinetics indicated that the lifetime of colored forms of 1 and 2 were several orders of magnitude longer than that of 3. The photochromic properties and reaction mechanism of the title compounds have been examined with steady-state methods on compounds 3-phenyl-3- [3-methylbenzothiophene-2-yl] -3H-naphtho [ phenyl-3- [benzofuran-2-yl] -3H-naphtho [2,1-b] pyran (2) and nanosecond laser flash photolysis techniques on compound 3-phenyl-3- [1,2-dimethylindol-3-yl ] -3H-naphtho [2,1-b] pyran (3). The influence of oxygen on transient spectra and decay kinetics of compound 3 has been investigated. Both excited singlet states and triplet states are involved in the photochromic mechanism of compound 3 . The influence of molecular structure on photochromic behavior has been studied also. Decay kinetics indicated that the lifetime of colored forms of 1 and 2 were several orders of magnitude longer than that of 3.