The invention discloses a collagen-lossless circular dechroming method of chrome-containing leather waste in leather working by ethylenediaminetetraacetic acid (EDTA) under photocatalysis. The method is characterized by comprising the following steps: mixing 100 parts of chrome-containing leather waste, 20 to 50 parts of EDTA and 100 to 500 parts of water; regulating the pH value to be 3 to 8; repeatedly dechroming the chrome-containing leather waste at the temperature of between 30 and 60 DEG C; further removing residual trace chrome in ultraviolet photocatalysis under the same condition after massive chrome is removed; regulating the pH value of the filtrate prepared in the performed process to be less than 0.5 with sulfuric acid, heating at the temperature of between 40 and 80 DEG C for 5 to 12 hours, cooling to separate EDTA crystal, and circularly using the EDTA crystal as a dechroming agent; and repeatedly using chromium sulfate in a liquid phase as a chrome tanning agent in leather working. According to the method, the structure of collagen in the leather waste can be well maintained, the chrome removal rate is over 98 percent, the process operation is simple, and the dechroming agent and collagen removed chrome can be recycled.