本文提供一個簡單的兩期兩要素模型，藉以說明資本移動限制與調整成本對自由化進行時程（timing）的影響。在經濟體系存在進口關稅的前提下，倘若資本無法立即於第一期跨部門移動，政府可能被迫改採緩慢自由化（gradual liberalization）的貿易政策來代替立即自由化（big bang），此即為次佳（second best）定理。由於增加財貨產出不一定要移動資本，所以資本重新配置所需之調整成本將會間接而非直接影響貿易開放的速度。當調整成本過高致使第二期本也不會移動時，減稅仍可改善各部門勞動配置而使單位效用達到最高，因此立即開放自由貿易反將變為福利極大化的最佳選擇。從理論推導及數值模擬的結果可知，當資本無法於第一期立即跨部門移動時，自由化進行時程將與調整成本大小有關；而當調整成本為零時，第一期資本能否自由移動將影響自由化最適進程。

　　　　　This paper studies the timing of trade liberalization in a small open economy, in which capital is sector-specific in the short run and is costly to move in the long run. In our two-period model with endogenous adjustment cost, if the intersectoral capital is specific initially and is mobile in second period, 'gradualism' will be better than 'shock'. The existence of adjustment cost may affect the speed of liberalization, but it does not imply a case for gradualism. When the cost of capital adjustment is infinite, a 'big bang' will be the welfare-maximizing choice. Furthermore, even if the reallocation of capital is costless, gradual liberalization will also be the optimal trade policy. Numerical simulations are also provided.