In order to eliminate the errors resulting from fluctuation of light source, the inner surface of integrating sphere is selected as reference in design of dual-optical path d/0 measuring condition on spectrophotometer. However, the repeatability and accuracy of measurement will decrease to a certain degree because of interference by diffuse reflected light of the test sample. This paper improves the dual-optical path d/0 measuring condition, composites LED as test light source, and configures a separated referenced white board substitute for inner surface of integrating sphere in the reference optical path. Then, the experiment is established. The results indicate that this improved dual-optical path d/0 measuring condition could effectively revise the errors caused by diffuse reflected light of test sample.