Objective To explore the influence of alimentary tract reconstruction after gastrectomy on the blood glucose level in patients with gastric cancers combined with type 2 diabetes mellitus. Methods From January 2004 to December 2009, the level of blood glucose and body weight before operation and 1,3,6 months after operation in 87 gastric cancer combined with type 2 diabetes mellims patients were retrospectively analyzed. These patients underwent different alimentary tract reconstructions,including 48 patients for Billroth I after distal subtotal gastrectomy (group A), 39 patients for esophageal Roux-en-Y jejunostomy after total gastrectomy (group B). Fasting blood glucose (FBG) level and body weight of these patients were compared. Results In group A, change of FBG before and after operation were not significant (P ＞ 0.05 ). The levels of FBG in group B were significantly lower in 1,3,6 months after operation [(6.7 ±0.8), (6.6 ±0.6), (6.8 ±0.7) mmol/L] than that before operation [(9.7 ± 1.4) mmol/L](P＜0.05). The lower value average difference of FBG at 1,3,6 months was significant between group A and group B (P＜0.05 ). In group B, 6 months after operation's total effective rate was 87.2% (34/39). Changes of body weight before and after operation in group A and group B were significant (P ＜ 0.05 ). But between two groups, the changes of body weight between 1,3,6 months and before operation were not significant (P ＞0.05).Conclusions Esophageal Roux-en-Y jejunostomy after total gastrectomy has obvious influence on FBG level in patients with gastric cancers combined with type 2 diabetes mellitus. It takes about 1 month to reveal the effect of operation and has nothing to do with weight loss.