The steady state and transient state absorption spectra and fluorescence spectra of N,N’-bis(2-hy-droxy-1-napbthylidcne)-1,4-phenyldiamme ( BNP ) in cyclohexane and acetonitrile were determined.The pho-tochromic mechanism was discussed In nonpolar solvents,BNP exists mainly in the enol form and has the absorption maximum in the UV region In polar solvents,however,both the enol and proton transfer tautomer are formed,but the farmer is the main one Fluorescence emissions result from the excited state of proton transfer product. The steady state and transient state absorption spectra and fluorescence spectra of N, N’-bis (2-hy-droxy-1-napbthylidcne) -1,4-phenyldiamme (BNP) in cyclohexane and acetonitrile were determined.The pho-tochromic mechanism was discussed in nonpolar solvents, BNP exists mainly in the enol form and has the absorption maximum in the UV region In polar solvents, however, both the enol and proton transfer tautomer are formed, but the farmer is the main one Fluorescence emissions result from the excited state of proton transfer product.