We present the absorptionof FTIR spectrumof pure polymethylmethacrylate polymer with different weight, pure laser dye fluorescein, and fluorescein dye doped PMMA polymer films with different doping ratio of fluorescein solution. All these films are prepared by casting method. It was found that the effect of increased doping ratio of fluorescein solution on FTIR spectrum led to increased the two distinct band (2989.66, 2951.61)cm-1 and decreased other bands. The role of added fluorescein dye clear at peaks (1635, 1581) cm-1 which corresponds to conjugated keton which increased with increased doping ratio.Also, the effect of carboxylic acid salt was shown at peaks (1481.33, 1448.61, 1388.75) cm-1with increased the dye solution added to polymer. The effect of decreased weight of PMMA polymer led to increased the intensity of the peaks that appeared in FTIR spectrum. This study is to determine the effect of change the weight of polymer and doping ratio of dye solution on FTIR spectrum, which have been evaluated and compared with other researches.