The invention relates to the technical field of hydrothermal synthesis of photocatalytic materials, in particular to a preparation method for a leaf-shaped silver chloride particle with a micron structure. The preparation method for the leaf-shaped silver chloride particle with the micron structure comprises the following steps: through hydrothermal reduction, mixing EG solutions of AgNO3, FeCl3 and PVP, which contain concentrated HCl; performing reaction for a certain time, and then cooling the solution; extracting a sample through centrifugation, and finally obtaining the high-content and axially-symmetrical leaf-shaped AgCl particle with the micron structure. The preparation method for the leaf-shaped silver chloride particle with the micron structure is simple in step and easy and convenient to operate; a larger proportion of concentrated HCl is added, the product is in a form of AgCl crystals and people usually use an Ag elementary substance obtained from the reaction composition and the preparation method; the scanning electron microscopy shows that the structure of the AgCl crystal particle with the micron structure has an unified axially-symmetrical triangular leaf shape; and a performance test shows that the leaf-shaped silver chloride particle with the micron structure has a good performance for photocatalytically degrading organic contaminants.