The telechelic macromonomer cross-linkable stabilizer (TMCS) was synthesized by the reaction of isocyanate-terminated prepolymer with methacrylamide and was successfully employed as a steric stabilizer and possible cross-linking agent in the dispersion polymerization of styrene. The urethane and methyl groups in TMCS are found in the spectrum of PS microspheres, and the reactive double bonds in TMCS disappear after polymerization with styrene. The qualitative analysis reveals that the symmetric molecular structure with vinyl group in TMCS takes part in the reaction with styrene, and it is proposed that the PS microspheres are substantially cross-linked. In reality, for the 100 wt % TMCS system, the PS is not totally soluble in THF, remaining as a translucent fully-swollen gel in THF. Thus, these qualitative structural investigations suggest that the TMCS serves as a reactive stabilizer as well as a cross-linking agent.