Objective To determine the safe doses of flushing fluid between groups during sequential infusion of thirty kinds of commonly used intravenous drugs, so as to provide a reference for clinical nursing. Methods Thirty kinds of commonly used intravenous drugs in clinical settings and capable of measuring drug absorbance by ultraviolet spectrophotometer were selected as experimental subjects, then they were dispensed into clinically commonly used Ⅳ fluids to simulate in vitro clinical infusion according to the instructions of drug administration.At the end of the infusion, 0.9% sodium chloride or 5% glucose injection consistent with the solvent was infused as the flushing fluid.Then a specimen of 1 mL was harvested, totalling 70, specimens.The absorbance of the specimens at different stages of flushing fluid volume was measured by ultraviolet spectrophotometer, and the concentration was calculated according to the standard curve, when it was zero, it demonstrated that the residual liquid in the infusion tube had been flushed clean. Results The volume of flushing fluid of the thirty intravenous drugs was 24-65 mL, of which 24-＜30 mL had 12 kinds, 30-＜40 mL had 10 kinds, 40-＜50 mL had 6 kinds, 50 mL and 65 mL each had 1 kind.The safe dose of flushing fluid between groups of twenty-two (73.33%) kinds of drugs was less than 40 mL. Conclusion In the sequential infusion of multiple intravenous drugs, when there is incompatibility or incompatibilities cannot be determined, it is necessary to use a safe dose fluid to flush the tube, which is conducive to the safety of clinical intravenous medication.