Gelator (G2-C12-G2) was synthesized successfully, the structure of which was confirmed by 1H-NMR and Mass spectra (MS). And G2-C12-G2 was used to modify PMMA by “in-situ” polymerization. The results of gel permeation chromatography (GPC) showed that Mn and Mw/Mn of the PMMA composite were barely influenced by the incorporation of gel. The results of dynamic mechanical analysis (DMA) showed that the modified PMMA had higher modulus, toughness and glass transition temperature (Tg) than pure PMMA. Furthermore the results of spectrophotometer showed that the transparency of modified PMMA was nearly the same as pure PMMA .