Based on the chemical bath deposition,semiconductor thin film cadmium sulfide (CdS ) for solar cells were prepared with thiourea,acetic acid, aqua ammonia used as the source of CdS and the buffering agent,respectively. The effects of different annealing temperature and coating CdCl2 methanol solution or not on CdS thin film are studied.XRD、SEM and the UV spectrophotometer were used to study the effect of the structure ,morphology and optical property of the deposited CdS film.The results show that coating CdCl2 methanol solution annealing treatment can obviously improve crystal quality of the film and its optical property.The best annealing temperature is 400℃.The annealing time is 60min.