本文建立一代表性資源回收構構的利潤極大化模型，以分玎廢機車胎與廢汽車胎資源回收成本不同的選擇性回收現象，即我們所定義的「排擠」效果。又為探討我國補貼機制，本文進一步將模型修正為政府介入與否（有無補貼）一兩階段社會福利模型，並以經濟圖形進行解析。結果發現，我國現行的補貼機制無法減輕「排擠」效果。而「排擠」效果出現時，若能調整補貼對象，情況便可改善，社會福利亦會增加，這或許是未來的可行方案。

　　　　　This paper uses an economic model to explain the so-called "crowding out" effect, which happens in the waste-tire recycling business. Due to some reasons, the recycling of waste motorcycle tires differs greatly from the recycling of motor tires. Most of the waste-tire recycling belongs to the latter. A revised model is employed to illustrate our current subsidy mechanism for the waste motorcycle-tire recycling can hardly lessen the "crowding out" effect. Borrowing form other countries' experiences, our results show that the problem may be solved and the welfare can be increased if the subsidy mechanism for the waste motorcycle-tire recycling spot is adjusted.