As for two sets of data, their qualitative distribution difference can be derived by using traditional statistical methods, while their mean value difference can be derived from quantitative difference(QD). A base-golden ratio logarithm is called as a golden logarithm, the authors found that a new natural constant can express the golden ratio, and its golden logarithm maintains unchanged, and called it as self-similar constant. The self-similar constant can not only express some fundamental physical constan...