本文將具有擁擠外部性特色的公共資本與不完全競爭特性的市場結構納入內生成長模型之中,更合理地說明生產性政府支出對經濟成長所造成的影響。在廠商數目是造成擁擠外部性的設定下,我們發現,生產性政府支出增加將會提高經濟成長率。其次,公共財的擁擠外部性愈大,將會造成生產性政府支出的經濟成長效果減緩。再者,獨佔力對於生產性政府支出的經濟成長效果則呈現不確定。另外,生產性的政府支出增加,可能使得短期私部門投資呈現過度調整的現象。而且,公共財擁擠外部性愈高時,過度投資的現象愈明顯。 This paper develops an endogenous growth model with the congestion of public goods and market imperfections to examine the macroeconomic effect of the government expenditure. We show that the productive government expenditure can stimulate economic growth. Moreover, the performance of government expenditure policies is crucially related to the market structure and the degree of market imperfections. It is also found that the key factor determining the transitional effect of an anticipated productive government spending on the investment is the degree of market imperfections.