The dissociation process of the sulfur trimer S３ in the low-lying excited states is investigated using ab initio method in this work. The dissociation limits of S３ are constructed. The calculation of transition moment between certain states indicates that the nonadiabatic process of conversion between different excited states occurs in the crossing regions of potential surfaces. Thus, we conclude that the nonadiabatic predissociation is important in the dissociation paths of S３ into S２+S.