Abstract: An improved protective bag structure, having a protective bag body made up of an insulating yarn layer interlacing with a reflective yarn layer with a multiple of small air-penetrating pores distributed at the surface thereon. The protective bag body also has an opening end and three other sealed edges wherein the opening end has a gathering string adapted thereto to collect and seal up the protective bag body thereof without any other extra string required. Via the opening end, the protective bag body can be easily and quickly applied onto fruit to shelter it therein or removed from it. The insulating yarn layer thereof can absorb the ultraviolet ray of sunbeams, and the reflective yarn layer can send back sunbeams to protect the fruit sheltered therein from the damage of sunburn, facilitating the benefits of high air-penetrability, well ventilation of humidity, heat resistance, heat-sinking capability, and bug-proof.