TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The method includes: (i) pre-treating chromium for recycling by soaking in alkali, filtering, soaking in acid and filtering; (ii) recycling the chromium element from the filtrate of alkali soaking and acid soaking; (iii) decomposing the leather into micro-molecular peptide and amino acid compound through enzyme method (acid or alkali method) and preparing into the compound organic fertilizer through condensing and packing; and (iv) optimizing the acid and alkali waste water so as to recycle water resource. The alkali soaking in the pre-treatment utilizes sodium hydroxide having 0.4-1.2% concentration, the ratio of the solid to the liquid is 1/20-1/10, the soaking temperature is 30-60 degrees C, and the soaking time is 2-48 hours. The acid soaking in the pre-treatment utilizes sulfuric acid having 4-20% concentration, the ratio of the solid to the liquid is 1/10-1/5, the soaking temperature is 30-60 degrees C, and the soaking time is 0.5-2 hours. The chromium is recycled by mixing the acid soaking liquid with the alkali soaking liquid, adding 0.8-1.2% of alkali for neutralizing, condensing, crystallizing, filtering and drying. The enzyme method decomposition utilizes enzyme having 0.8-2% concentration, the ratio of the solid to the liquid is 1/20-1/10, the enzyme digesting temperature is 45- 70 degrees C, and the reacting time is 2-12 hours. The alkali method decomposition utilizes alkali having 1-20% concentration, the ratio of the solid to the liquid is 1/10-1/3, the reaction temperature is 50-100 degrees C, and the reacting time is 2-24 hours. The acid method decomposition utilizes sulfuric acid having 10-40% concentration, the ratio of the solid to the liquid is 1/1-10/1, the reaction temperature is 50-100 degrees C, and the reacting time is 1-12 hours. Preferred Components: The enzyme for the enzyme method decomposition comprises alkaline protease, papain, bromelain and trypsin. ACTIVITY - Fertilizer.