After analyzing historical progress of European monetary unification, we find out that most member states in Euro area prefer to choose fixed exchange rate regimes. We classify fixed exchange rate regimes into three types in terms of cooperation quality, and take a model to make .some comparisons among these three regimes. Findings shows that fixed exchange rate regime in terms of common money in Europe with the highest cost of reneging is more robust and more insensitive to speculative attacks. Therefore, the threats to exit from Euro area are ineonvincible after the frustration of Constitutional Pact of European Unions and the progress of European monetary unification is unavoidable and also irreversible.