Abstract: Contents of Fe(Ⅲ) and Cu(Ⅱ) in saturated steam of thermal power generating unit were determined by IC with direct sample introduction in large volume. The sample (100.00 mL) was digested with 1 mL of HCl (1+9) and 1 mL of 10 g·L-1 ammonium persulfate solution. The IonPac CS5A column was used for separation, and a mixed solution containing 3.5 mmol of 2,6-pyridyldicarboxylic acid, 66 mmol of KOH, 83 mmol of formic acid and 5.6 mmol of sodium sulfate in a total volume of 1 liter was prepared (adjust its acidity to pH 3.7) and used as mobile phase for elution. VIS-spectrophotometric detector at 505 nm was used in the determination. Linear relationships between values of peak height and mass concentration of Fe(Ⅲ) and Cu(Ⅱ) were kept in the range within 15 μg·L-1 and 50 μg·L-1, with detection limits of 0.058 and 0.073 μg·L-1 respectively. The proposed method was applied to the determination of Fe(Ⅲ) and Cu(Ⅱ) in sample of saturated steam; values of recovery and RSD′s (n=8) found were 100%, 1.3% for Fe(Ⅲ) and 90.5%, 1.8% for Cu(Ⅱ), respectively.