Based on the idea of the hyperbola function expansion method, some analytical solutions of the modified Korteweg-de Vries (mKdV) equation are obtained by introducing new expansion functions. One of the single soliton solutions has a kink-antikink structure and it reduces to a kink-like solution and bell-like solution under different limitations. The stability of the single soliton solution with double kinks is investigated numerically. The results indicate that the soliton is stable under different disturbances.