This invention relates to a method for decolorizing a dyed denim fabric through a dry ozone process to obtain an aesthetically pleasing decolorized look or fashionably faded look in the denim fabric. The method comprises three dry ozone treatment processes used alone or in combination thereof. The first dry ozone treatment process includes wetting a denim textile product with water and oxidizing it with ozone. The second dry ozone treatment process includes spraying water to desired areas of the textile product and oxidizing it with ozone. The third dry ozone treatment process includes loading the denim textile product and wetted cotton fabric scraps into a drum, and oxidizing them with ozone.