Abstract: The study of feeding regimens (pasture, grazing supplementary and confinement) on slaughter performance, meat quality in the longissimus dorsi muscle of Sunit sheep were determined. Afterwards, quantitative classification of muscle fiber types was conducted by ATPase histochemical staining and real-time fluorescence quantitative quantification to explore the difference of feeding patterns on types composition of muscle fiber , in order to explore the internal reasons for the difference of meat quality in different feeding methods. The experimental results indicated that the slaughter performance indexes such as total weight gain, net meat weight, net meat rate, slaughter rate and meat production rate, and carcass quality indexes such as backfat thickness and carcass weight of the the grazing supplementary and confinement feeding patterns were increased remarkably than those of the pasture pattern (P < 0.05), the ratio of bone to meat of the pasture pattern was significantly higher than that in confinement and grazing supplementary feeding patterns (P < 0.05). The pH_{24 h} of the confinement pattern was remarkable lower than that of the pasture and grazing supplementary feeding patterns (P < 0.05), and the shear force of the pasture pattern was remarkable lower than that of the confinement pattern (P < 0.05). The diameter and area proportion of typeⅡb muscle fiber in pasture pattern and grazing supplementary feeding pattern were significantly higher than those in confinement pattern (P < 0.05), and the gene expression of MyHCⅡb mRNA was significantly lowr than that in confinement pattern (P < 0.05). The diameter, cross section area of typeⅠandⅡa muscle fibers, the enzyme activity of LDH in the confinement pattern were significantly elevated than those in the pasture pattern (P < 0.05), the number and area percentage of Ⅱa, the gene expression of MyHCⅠmRNA, the muscle fiber density and the enzyme activity of MDH in the confinement pattern were markedly lower than those in the grazing supplementary feeding and pasture pattern (P<0.05), the genes expression level of MyHCⅡx, MyHCⅡa mRNA and the enzyme activity of SDH in confinement pattern were reduced significantly than those in pasture pattern (P < 0.05). Therefore, different feeding regimens of Sunit sheep have their own advantages, and the slaughter performance and carcass quality of Sunit sheep under confinement and grazing supplementary feeding are better. Pasture and grazing supplementary feeding have better meat quality due to their ability to enhance muscle oxidative metabolism and higher proportion of oxidized muscle fibers.