Using a non-local symmetry of the Kaup-Kupershmidt (KK) equation, we find a new exact solution in two different ways. Firstly, using the standard prolongation approach, we obtain the finite Lie B?cklund transformation and the single soliton solution of the KK equation. Secondly,combining some local symmetries and the nonlocal symmetry, we get the group invariant solution and obtain the new soliton solution of the KK equation.