Abstract: OBJECTIVE The self contrast and correction factor method was established to measure the content of 4-isobutylbenzoic acid in ibuprofen. METHODS Prepare series of solutions containing 4-isobutylbenzoic acid and ibuprofen for determining the correction factor. Inject the solutions into two different equipments and record the chromatogram. Measure the peak area of 4-isobutylbenzoic acid and ibuprofen and calculate the correction factor. Use the slopes of linear equations to determine the correction factor between 4-isobutylbenzoic acid and ibuprofen. Then, validate the analytical method to ensure that HPLC method for the determination of impurity 4-isobutylbenzoic acid in ibuprofen meets the requirement for the intended analytical applications. At last, compare the results determined by the external standard method and the self contrast and correction factor method with statistical software SPSS13.0. RESULTS The correction factor between 4-isobutylbenzoic acid and ibuprofen is 0.129, and there is no statistical difference between the contents of impurity 4-isobutylbenzoic acid in ibuprofen determined by the two methods. CONCLUSION The self contrast and correction factor was found to be accurate, linear, sensitive and stable.