The invention discloses preparation and application of a 3-substituted-N-hexyl phenothiazine derivative shown in a general formula (I). In the formula, R is malononitrile group, 1, 2, 4-triazolo [1, 5-a] pyrimidyl, spiropyranyl, 3-dicyanomethylene-1, 5, 5-trimethylcyclohexenyl, 1, 3-diethyl-2-thiobarbituric acidyl, N, N-dimethylaminophenyl, p-nitrobenzophenone or 2, 4, 6-trimethyl-3, 5-dicyanopyridyl. All the compounds have fine solubility and thermostability and can be applied to flat-panel displays as red electroluminescent materials.