A serum prostate-specific antigen (PSA) measurement method was studied using immunochromatography-based colloidal gold-marked test-strips and characteristic spectral absorption method. Some LEDs in the range from 520 to 535 nm irradiated the test-strips sampled by PSA, and then a photodiode in the range from 520 to 540 nm measured the reflex light at the specific area. Accordingly, the absorbency of the strip could be calculated, then the relationship between PSA level and strip absorbency could be ascertained by linear fit method. The experimental measurement system was calibrated by different PSA standard solutions in this research. As a result, in the range between 5 to 50 ng·mL-1, the levels of PSA have a linear relationship with the absorbency of test-strips. Some experiments were completed by 21 different PSA standard solutions within that range, and then the correlation coefficient of the results is equal to 0.910, which proves that the proposed method for serum PSA level measurement is feasible.