When PPP (Public Private Partnership) mechanism is gradually accepted by domestic academic and bureaus of different levels, PPP is not only used in municipal infrastructures. To get closer with international trend, PPP is also applied at Public Schools. Due to the nature of common weal, Public Schools cannot refinance through service charge from delivering education activity. Therefore, governmental subsidy is necessary throughout the life circle of PPP public schools. Many factors have impact to the governmental subsidies, and service quality is the key among them. Focus on service defects and stakeholders’ satisfaction, by means of theoretical and mathematic models, this paper will study the relationship between governmental subsidies and service quality.