The morphological change of St/DVB crosslinked gels during chloromethylation was studied by fluorescence spectroscopy using St/DVB crosslinked and hypercrosslinked gels as control samples. It has been found that with increase of chlorine content, the excimer emission band (~325nm) approaches to vanish, while the intensity of multi-ring aggregate emission band (~420nm) quickly reaches a maximum, and then decreases sharply accompanied by appearance of a new broad band centred at ca 488nm which roughly coincides with the typical emission band of hypercrossllinked St/DVB gels. Mearwhile, the result of IR measurement suggests that methylene bridge between phenyl rings forms and increases with chloromethylation process. These results are explained in terms of a side reaction of post-crosslinking, which densifies the loosely crosslinked networks and undoes the densely entangled microgel nuclei. As a result, the morphology of the crosslinked gels becomes more homogeneous with chloromethylation. The morphological change of St / DVB crosslinked gels during chloromethylation was studied by fluorescence spectroscopy using St / DVB crosslinked and hypercrosslinked gels as control samples. It has been found that with increasing of chlorine content, the excimer emission band (~ 325 nm) approaches to vanish , while the intensity of multi-ring aggregate emission band (~420 nm) quickly reaches a maximum, and then decreases sharply accompanied by appearance of a new broad band cent at ca 488 nm which roughly coincides with the typical emission band of hyperlinked St / DVB gels . Mearwhile, the result of IR measurement suggests that methylene bridge between phenyl rings forms and increases with chloromethylation process. These results were explained in terms of a side reaction of post-crosslinking, which densifies the loosely crosslinked networks and undoes the densely entangled microgel nuclei As a result, the morphology of the crosslinked gels becomes more homogeneous with chloromethylation .