Non-metal reusable bag closing clamp, namely a bag closing device which consists of two parts, a half moon shaped piece and a rod when they are placed together with the bag opening in between, the bag opening effectively is sealed by the clamping action of the 1/2 moon shaped piece closing on the rod; both the bag and clamp are made with polypropylene plastic and can withstand 125 degrees of heating by steam for sterilization and to avoid contamination; the clamps are used for bags that grow mushrooms; the clamp clamps on the outside of the bag and avoids contaminating the substrate inside of bag and for processing, the bag can be partly clamped with small opening to allow bag expansion during autoclaving, quickly sealed and quickly opened to allowing spawning and resealed