Abstract: The semitendinosus (SD) and biceps femoris (BF) of Wuzhumuqin sheeps from 1 to 18 month old, were employed, and the histochemical methods were used to analyse the changes of diameter of muscle fibers and intramuscular connective tissue and muscle fiber types during the growth of Wuzhumuqin sheep.Results showed that, in SD and BF, the diameter of muscle fibers were increased from 1 to 9 month old, decreased from 9 to 12 month old, after then it was increased at 18 month old.The thickness of endomysium was increased, however the perimysium was thickened from increased from 1 to 9 month old, decreased from 9 to 12 month old, after then the thickness of perimysium was increased gradually.TypeⅠ in the BF and SD, had big change, they dropped at 9 and 18 month old.In the SD, the percentage of Type Ⅱa got the lowest at 12 month old, while TypeⅡb had the highest level.In the BF, the percentage of TypeⅡa had no significant difference among the 1, 9, 18 month old, including 3 month old and 6 month old (p>0.05) .TypeⅡb had the highest level at 12 month old.