Disclosure quality is very important to listed companies and capital market. Based on factor analysis method this paper presents a disclosure quality index that is well verified by the assessment results of Chinese Shenzhen Stock Exchange. The index focuses on three aspects: corporate governance, firm structure characteristics and financial situation. The index has three advantages compared with previous researches: number of factors is less than other measurement methods; all weights of the variables are objective and avoid subjective errors; the results may assist in determining the quality disclosure and explaining the variation of current and prospective extent.