Effect of interchain and intrachain interactions of porphyrins on the luminescence property of a novel porphyrin side-chain polymer, poly[porphyrin acrylate-acrylonitrile](p[(por)A-AN]) is studied. By femtosecond time-resolved photoluminescence spectroscopy, transient photoluminescence dynamic process in p[(por)A-AN] is measured. The luminescence efficiency and lifetime are decreased upon going from the pure films to the dilute blended films form 450 ps to 1.3 ns for the lifetime, which are enhanced and increased from ～26 ps to ～36 ps for the lifetime by increasing the concentration of the porphyrin sidechain groups from 8% to 15%. The energy transfer without irradiation between the porphyrin chromophores and the rotation of the porphyrin side-chain groups in the p[(por)A-AN] molecules play important roles in the luminescence dynamics in the p[(por)A-AN] films.