本文建立一個兩國模型，在模型中有一外國廠商欲選擇FDI或出口模式進入地主國市場，並與地主國之n廠商從事Cournot競爭。面對地主國實施之污染稅政策，設廠在地主國之所有廠商皆使用相同污染防治技術。本文發現，當貿易成本較高，而且污染的防治技術較有效率時，提高污染稅率可能使外國廠商到地主國FDI，此外，在某些參數條件下，提高污染稅讓外國廠商移出地主國反而會造成地主國的環境品質下降，而且也可能提高地主國之消費者剩餘。因此，污染稅率之調整與污染防治技術效率及貿易成本的交互作用對外國廠商選擇進入模式及其相關的福利效果具有關鍵性的影響。

We set up a two-country model in which a foreign firm chooses FDI or exporting to enter the host market, and plays a Cournot competition game with 11 host firms. Facing the host country's emission tax policy, all firms located in the host country use the same abatement technology to abate emissions. The major findings are as follows. When the trade cost is high and the abatement technology is efficient, a higher emission tax rate may encourage FDI. Moreover, under plausible parameters, raising the emission tax to drive the foreign firm out of the host country will be detrimental to environmental quality but raise consumer surplus in the host country. The interaction of the abatement technological efficiency and trade cost with emission tax plays a key role in the entry mode of the foreign firm and the associate welfare of the host country.