The objective of this study was to investigate the effect of long-term grazing sheep in cotton stubble on variation of biochemistry components and free gossypol residual in the blood. The survey found that 15% ewe of grazing group suffered miscarriage or premature birth, compared with the captive group ewes without this phenomenon. Blood test result shows that the free gossypol concentration in serum of grazing group was significantly higher than in indoor captive feeding group (P<0.01). In order to ensure the health of sheep grazing on cotton stubble and improve breeding rate, there is a need to do further reasonable research of grazing and feeding methods.