In order to study the effects of chronic alcohol intake on serum glucose, insulin and glucose tolerance test (GTT), a oral administration of alcohol solution (6 ml/kg.d) in different concentration (10%, 30% and 50%) is given to rats for 60 days. The results showed that the fast serum glucose of rats in the groups orally administrated with 30% and 50% alcohol solution increases obviously in comparison with that in control group. There exist abnormalities in 1 hour, 2 hour and, 3 hour GTT (P < 0.05) in these groups and the difference in gender in both groups is statistically significant. It is also shown that the level of serum insulin of rats decreased along with the increase of alcohol dosage and is significantly lower in the group of rats administered 50% alcohol solution than that in the normal control group (P < 0.05). These results demonstrated that chronic alcohol intake causes the increases of fast serum glucose and abnormality of glucose tolerance test (GTT), and likely, the final abnormality of glucose metabolism in which the decrease of insulin secretion might be one of the contributing factors to the pathogenesis.