The invention discloses a dung-urine separator and a metabolism cage for livestock nutrition research; the dung-urine separator comprises a bottom plate and side plates arranged on two sides of the bottom plate; the bottom plate and the side plates form a groove shape; the front portion of the bottom plate is provided with an urine outlet; the height of one end, close to the urine outlet, of the bottom plate inner surface is lower than that of the other end, far away from the urine outlet, of the bottom plate inner surface; the height of one end, close to the urine outlet, of the side plate inner surface is lower than that of the other end, far away from the urine outlet, of the side plate inner surface; the middle portion and rear portion of the bottom plate inner surface are provided with dung baffle plates, and the bottom of the dung baffle plates are provided with holes; a forage baffle plate is arranged above the urine outlet. The dung-urine separator can fully separate the livestock dung from urine, thus solving dung and urine separate collection problems, and providing guarantee for experiment results.