It is well-known that the classical integrable systems adapt solitons, solitons reflect various nice properties of integrable systems. The existence of non-smooth solitons is an nontrivial feature of integrable systems with nonlinear dispersion. In this talk, we shall discuss stability of non-smooth solitons of integrable systems with nonlinear dispersion. First, we shall study the orbital stability of peaked solitons of scalar equations. Second, orbital stability of peaked solitons to systems is discussed. Finally a Liouville property to an integrable system is investigated.