Abstract: Artificial grassland is main rangeland in Karst region in Yunnan-Guizhou Plateau. In this paper, nutritional value and conversion efficiency of grasses of two artificial grasslands were tested through grazing test, feeding experiment, and digestion and metabolism trial. Testing under the same grazing pressure, grazing experiment showed that soil nutrients, trace elements and forage yield of Yongshan Artificial Grassland was significantly lower than Xundian Artificial Grassland, but no significant difference in nutritional content between the two artificial grasslands were detected. Feeding trial showed that grass usage efficiency by sheep on Yongshan Artificial Grassland was higher than Xundian Artificial Grassland, digestibility and deposition rate of mineral trace elements in sheep grazing on Yongshan Artificial Grassland were significant higher than Xundian Artificial Grassland. Digestion metabolic test showed that nutrient content including crude protein, crude fat, crude ash, crude fiber, nitrogen free extract in grasses of Xundian Artificial Grassland were higher than Yongshan Artificial Grassland. Comparison of digestive rate, feed intake and body weight gain of sheep gazing on the two artificial grasslands showed the same trend with nutrient content. The above results indicated that, a high conversion efficiency was produced by livestock grazing on Yongshan Artificial Grassland, where was a relatively barren field with a lower forage production than Xundian Artificial Grassland. According to the results, we proposed to feed on livestock after maturity of grasses, and supplementation of certain trace elements. At the same time, we proposed, grass and artificial grassland nutritive value evaluation needs not only the determination of its nutritional content, but also its final value, namely, animal weight gain, because conversion efficiency of livestock directly affects the efficiency of grassland animal husbandry. The output of artificial grassland can only be evaluated accurately by combination of nutrition value evaluation and livestock conversion efficiency estimation.