This invention is directed to a sterilization method of contaminated areas with biological agents by making use of the acidic ozone water that very effectively kills spores of Bacillus atrophaeus, thereby demonstrating the capability of sterilizing a large surface-area in a very short time and reinstating the contaminated environment as free from toxic biological agents. The effective sterilization of the acidic ozone water is due to synergic benefits derived from the combination of ozone and acidity. The acidic ozone water can also effectively kill other ordinary microbes of viruses, bacteria, and fungi, hence being applicable to agriculture, seafood and livestock industries for the preservation of various products as well as being useful in hospitals or other germ infested areas for disinfections. Particularly, the acidity and ozone in the seawater sterilize microbes effectively, demonstrating a potential for the sterilization of a large amount of seawater in a short time. After the decontamination process, the acidic ozone water disintegrates into water and oxygen without any trace of harmful materials to the environment.