It has been worshipped by the western politicians,strategists and diplomats in modern times,for they believe that balance of power can bring peace to international society under "a natural state.

The formation of the new balance of power in the European Setup is a premise for the interference of the German-Russian-French triple cooperation, while the interests of the three individual countries in strategy and security are the basic dynamic behind the tempo.

While he was in charge of the British foreign affairs, he adopted the diplomatic policy of balance of power and hegemony toward the mainland of Europe, far - east and near - east regions for the purpose of seeking for the new and developing foreign policy on the basis of British vested interest, which exerted profound and lasting influence on the British diplom.

Besides,it had broken the fragile balance among European countries.

Though the equilibrium could not be maintained or rebuilt,Britain tried to adopt an anti-balance policy to break out of this situation.

The former pursues power balance while the latter emphases the partnership of international relationship.

The practice and theory of equilibrium emerged a long time ago in the West,but the strategy of equilibrium is really the case in modern times.

Henry Kissinger s doctrine of Golden mean ,whose fundamental content is of “limit” and “transcendence”, is the philosophic fundation of his thoughts of equilibrium strategy based on his theory of the balance of powers, which stems from his elaborate study on the Europe diplomacy in the early part of 19 century.

However these studies in China have just started, so I will dissertate Thucydides international relationship theories from power and advantage, equipollence and conflict theories.

While making the physicochemical models as clear as possible, the advantages of using the methods of "potential of mean force" are stressed and formulas for using these methods are given by making use of the second order reduced density matrices.