OBJECTIVE To establish a method for the determination of related substances in gefitinib and gefitinib tablets, evaluate the quality evaluation of products from different manufacturing enterprise and reserve methods for the new version of the Chinese Pharmacopoeia. METHODS HPLC experiment was performed on a column of CAPCELL PAK C₁₈ MGⅡ (4.6 mm×250 mm,5 μm) with the mobile phase of 1% ammonium acetate solution (adjust pH to 6.20±0.05 with glacial acetic acid) (A)-acetonitrile (B) with gradient elution. The flow rate was 1.0 mL·min^-1, the column temperature was maintained at 30 ℃, and the detection wavelength was set at 247 nm. The injection volume was 20 μL. RESULTS Gefitinib and 17 impurities showed good linear relationships with the peak area in the range between the LOQs and 0.2% of the principal component (r>0.999 0). The recoveries are between 89.4% and 108.6%. The LOQs are between 0.5 ng and 4.6 ng (equivalent to 0.002% to 0.02% of the principal component), and the LODs are between 0.1 ng and 1.0 ng (equivalent to 0.001% to 0.005% of the principal component). The results showed that the main impurity detected in gefitinib raw material was impurity B, while the main impurities detected in gefitinib tablets were impurity B and impurity Ⅴ. CONCLUSION This method is efficient, sensitive, accurate, and has good durability. It can be used for the quality control of impurities in gefitinib and gefitinib tablets. And it provides a reliable method for updating national pharmacopoeia standards.