Transient fluorescence dynamics of a new kind of porphyrin side-chain polymer film ［poly［porphyrin acrylate-styrene］ (P［(por)A-S］) at high excitation density has been measured by using time-resolved fluorescence spectroscopy. The fluorescence decay becomes more rapid with the increase of the interchain polymer concentration. The origin of the concentration quenching has been analysed according to the Frster-type bimolecular annihilation theory. The theoretical analyses are in good agreement with the experimental results. Rosults show that, in the case of high excitation density, the Frster-type bimolecular annihilation is the main reason of the fast initial luminescence decay and the low luminescence efficiency of the porphyrin side-chain polymers.