The stability of lattice solitons is examined on computer. The three-body collision is found to preserve the initial identity of individual solitons participating the three-body collision. Large deformation provokes a soliton to split into two solitons and a train of ripples. The stability of solitons under random disturbances is examined on computer. The speed of a soliton decreases gradually when large disturbance is given initially on the medium, and thus the soliton is subjected a viscous damping. Furher it is surmised from the experiments that there exists a critical value of the energy of the disturbance given to the medium, under which the soliton is stable and the speed is not affected by the presence of the disburbance.