This utility model provides an improved mirabilite bag, which solves the problems of easy agglomeration and leakage of existing mirabilite when used. The bag body is formed by folding and sewing breathable cloth in half. One end of the bag body has a bag opening, which is divided into six accommodating chambers. The three accommodating chambers have zippers at the opening, and a layer of waterproof cloth is set on the outer side. The distribution of nitrate in the bag is more uniform and less prone to leakage.