【Objective】 To explore the effects of massive intraoperative RBC transfusion on multiple clinical test indicators and prognosis of patients, underwent tumor surgery in order to provide evidence for rational blood transfusion and effective intervention of complications caused by massive blood transfusion in tumor patients. 【Methods】 A total of 208 patients who underwent tumor resection in our hospital from January 2019 to December 2020 and received intraoperative RBC transfusion(>10 U) were selected as the study subjects. According to the amount of blood transfusion, they were divided into group A: 10~15 U, 144 patients; Group B: >15~25 U, 48 people; Group C: >25 U, 16 people. Data of liver function, coagulation, electrolyte, platelet count and short-term prognosis were collected and compared among 3 groups before and after surgery. 【Results】 No significant difference was noticed in patient pre-operation variables including ALT (U/L), AST (U/L) and TBIL (μmol/L) among three groups recieved massive blood transfusion (P>0.05), while AST was significantly lower than that after operation (P<0.05) : 105.33±238.18 vs 113.50±185.04 vs 291.25±457.33 (P<0.05). After operation, PT (s) (14.12±2.10, 14.79±2.67 and 16.10±4.06), INR(1.25±0.20, 1.31±0.26 and 1.44±0.38) and APTT (s) (30.52±5.63, 34.57±12.80 and 34.80±10.49) extended significantly than those before operation (P<0.05), while Plt (×10⁹/L) decreased significantly (142.32±70.07, 100.04±57.50 and 85.40±41.10)(P<0.05). After operation, serum K⁺ and Ca²⁺ decreased significantly, Na⁺ and Cl^- increased significantly, and pH value decreased (P < 0.05). Hospital stay of group C (d) was 33.73±34.62 vs 17.74±14.83 vs 20.92±17.69 (P<0.05). The mortality rate was 2.8%(4/44) vs 6.3%(3/48) vs 18.8%(3/16)(P<0.05), and mortality rate of group C was higher than the other two groups. 【Conclusion】 Postoperative dysfunction of liver and coagulation in tumor patients may be related to intraoperative RBC transfusions and consequent acid-base imbalance and electrolyte disturbance. The more the units of RBC transfused, the more abnormal the patients' clinical indicators, also the longer the hospital stay and the worse the short-term prognosis.