N-N/- di-phenyl guanidine (DPG) in compination with cyclohexyl benzothiazole sulfenamide (CBS) is widely used as an accelerator for the vulcanization of silica filled solution styrene butadiene rubber (S-SBR). The vulcanizate thus obtained exhibit excellent mechanical properties, good dynamic properties and also good againg resistance property. However, the use of DPG is a bit restricted of late being reported to be a potent carcinogenic compound and, hence, the effective substitution for DPG by safe alternative has been extensively explored. In this study, we systematically study the effects of naturally occuring amino acid L-cystine (L-cys) and its derivative L-cystine dimethyl ester dihydrochloride (ELCH) as environmental friendly co-accelerators for the vulcanization of silica filled S-SBR.