The invention relates to a method for treating birch bark. The method comprises the following steps: (1) peeling fresh birch bark, cleaning the surface, suffocating for 1.5-2 hours by a steamer, and then cooling naturally; (2) preparing a treatment solution, mixing 3.2-4 parts of polyethylene glycol, 6-8 parts of glycerinum, 4.5-6.8 parts of potassium nitrate, 1-1.8 parts of pine-seed oil, 1.5-2.4 parts of chlorinated paraffin and 25 parts of water evenly so as to prepare the treatment solution; (3) putting birch bark treated in the step (1) into the treatment solution prepared in the step (2), soaking for 2-3 days, flushing clean with clear water after treating is completed, then suffocating for 0.5 hour by the steamer, taking out, cooling to normal temperature at the cooling speed of 2 DEG C / min. The method for treating birch bark for bark pictures is simple, and is convenient to use; the treated birch bark is good in stability and is easy to color.