The realization of Wagner’s Law is the manifestation for the government of each country to reach its functional objective. In order to furthest realize government functional goal, the government of each country uses realizing way of imbalanced budget which financial expenditure increases firstly and then financial revenue increases, macro-tax revenue continuously fluctuates but demonstrates the rising trend as a whole while governmental expenditure continues to increase. According to realizing way and process of Wagner’s Law in developed and developing countries, the continuous increase of public expenditure is a gradual process and is positively related to economic development and national income of a country. Thus, Chinese Government should pay attention to adverse influence of excessive debt or tax on economic development when implementing financial policies.