Abstract: Objective To observe the changing rules of resting energy metabolism(REM) in perioperative elderly patients with gastrointestinal tumor. Methods Seventy-three elderly patients with gastrointestinal tumor at the age of 65-80 years were included in this control study.Their REM was assayed before and 3-5d and 7-10d after surgery by indirect calorimetry(MedGem).Their body height,body weight,body mass index(BMI),biochemical indications,albumin and C-creative protein(CRP) level were measured.Their nutritional status was tested following the mini nutritional assessment(MNA) score. Results No significant difference was found in REE among the patients before and 3-5d after surgery(4 869.07±432.31)kJ/d vs(4 629.10±421.68)kJ/d in males,(4 062.12 ±502.49)kJ/d vs(3 892.63± 488.29)kJ/d in females,P>0.05).The REE was significantly lower in male and female patients 7-10d after surgery than before and 3-5d after surgery(3 443.15±385.02)kJ/d vs(4 340.22±418.82)kJ/d and(4 600.47± 434.45)kJ/d,(4 137.11±347.21)kJ/d vs(5 012.36±455.15)kJ/d and(5 091.66±421.89)kJ/d in male patients,and(3 766.56±388.08)kJ/d vs(4 180.08±305.86)kJ/d and(4 477.11±416.47)kJ/d in female patients,(P<0.05).The hemoglobin level and total number of lymphocytes were significantly lower in male patients 3-5d and 7-10d after surgery than before surgery(131.07±24.18)g/L and(125.08±23.82)g/L vs(147.79±14.82)g/L,(1 363.95±570.76)/ml and(1 316.78±589.66)/ml vs(1 667.98±600.15)/ml,(P<0.05).The BMI and MNA score were significantly lower in male and female patients after surgery than before surgery(22.02±2.07)kg/m² and(21.45±2.89)kg/m² vs(23.11±2.11)kg/m²,(20.77±2.08)kg/m² and(20.06±2.16)kg/m² vs(21.04±1.99)kg/m² in male patients,20.58±6.22 and 20.92±8.15 vs 22.98±5.48,20.33±9.16 and 19.98±6.88 vs 23.12±6.26 in female patients,(P<0.05). Conclusion The REM of elderly patients with gastrointestinal tumor tends to decrease after surgery,which may be related with the decreased BMI,hemoglobin,total number of lymphocytes and MNA score.