The indoor experimental study was on a large common species of filamentous green algae in the North Lake beach of Chongming Island - bristles algae liquid produced by algae growth during the photodegradation of colored dissolved organic matter (CDOM) spectral characteristics change. Absorption coefficient a (355) in the degradation experiment was reduced 27.44% , however , in the control experiment , a (355) was only 1.61% lower. In the photodegradation process of degradation experiments and control experiments, the values of M and S were increased to the different extent and the increased value of the former was higher than the latter. By using three-dimensional fluorescence spectroscopy (EEMS), the detected peak value of protein-and humic fluorescence in control experiments was little changed, while significantly increased in the degradation experiments. By the analysis of parallel factor model (PARAFAC) combined with three-dimensional fluorescence excitation - emission matrix data (EEMS), the three-component CDOM: C1, C2, C3, respectively were relative to humic fluorescence peaks A, C, and protein-like fluorescence B. In the degradation experiments, small changes were in the components of C1, however the components of C2, C3 compared with those in the control group were increased by nearly 2 times. All results showed that the photodegradation process of bristles algae liquid can cause changes of the CDOM in the structure and content, easier to produce small molecules and weak aromatic CDOM.