In order to observe electrolyte changes before and after scheduled abdominal surgery and effect of prompt potassium supplement on the recovery of gastrointestinal function, electrolytes in 69 patients were tested before and after surgery, and the recovery of the gastrointestinal function was observed.The results showed that after surgery the levels of K＋, Na＋ and Cl＋ were decreased dramatically (Ｐ＜0.05) but still within the normal range, with no distinctive change in Ca２＋ and Mg２＋. No correlation between the amount of blood transfusion and potassium was detected. Prompt potassium supplement contributed to the quick recovery of gastrointestinal function.This suggests that with normal renal function, blood transfusion during the operation will not cause hyperkalemia, potassium supplement might begin on the first day when the patient begins to urinale.