Let Sn denote the symmetric group of degree n with n ≥ 3,S ={cn =(1 2 … n),cn-1,(1 2)} and Tn =Cay(Sn,S) be the Cayley graph on Sn with respect to S.In this paper,we show that Γn (n ≥ 13) is a normal Cayley graph,and that the full automorphism group of Γn is equal to Aut(Γn) =R(Sn) × <Inn(φ)> ≌ Sn x Z2,where R(Sn) is the right regular representation of Sn,φ =(1 2)(3 n)(4 n-1)(5 n-2)… (∈ Sn),and Inn(φ) is the inner isomorphism of Sn induced by φ.