本文試圖找出十八世紀末至十九世紀前半之間，導致「臺運」逐漸衰退的結構性因素，透過臺灣與漳泉米價差距的檢討，以及臺灣島內米價所存在的地區性差異，發現十八世紀中葉臺灣米穀移出的價格低廉這一背景，在1830 年代中期出現了供需地與價格賤貴背離的現象。米價因素與「臺運」運作的商船、正口航路等種種條件相互作用，導致了「臺運」逐漸發生變化。 十八世紀臺灣的米穀價格低廉，民間商人利用臺灣與漳泉之間存在的米價差距，在官方政策允許下從事米穀交易；同時官方也依賴民間商船配載「臺運」官穀，達到遂行公務的目的。「臺運」的流通結構，一方面依附於民間交易的成立，同時也受限於官方所制訂的對渡正口、航路與船舶等種種政策。 林爽文事件結束之後的乾隆53、54 年（1788、1789）之間，臺灣南部出現了高於漳泉的米價，意味著前往南部鹿耳門一口從事米穀交易難以獲利；但在此同時，北部由於米價較南部低，造成商人利用漁船、小船前往南部以外的中、北部地區經商。雖然嘉慶年間的臺灣南北米價普遍下跌，但是以非商船的名義前往臺灣中、北部從事米穀交易，可以省卻回程的「臺運」配穀，逐漸造成人為的規避「臺運」。道光年間，尤其在1830 年代中期，臺灣的南北米價同時高昂，與漳泉的同類米價並沒有太大的價格差異，在獲利減少的情況下，出入私口又可規避「臺運」的負擔，因此前往正口的民間商船減少，導致了依賴民間商船由正口配運的「臺運」這一流通結構逐漸鬆動崩解。這一過程，顯示了十八世紀末至十九世紀上半葉所同樣出現的「臺運」衰退問題，可說是在不同時期的背景下相異因素作用的結果。

This article aims to analyze the decline of “Tai-yun” circulation structure. “Tai-yun” refers to the transport of rice, collected as land tax in Taiwan, to Qing troops and their families stationed in Fukien. By comparing the difference in rice price between Taiwan and Quan-zhou Prefecture, as well as that in various parts of Taiwan, this article examines the role played by rice price in “Tai-yun” and its transformation. During the 18th century, rice in Taiwan was inexpensive. Merchants from China took advantage of the price difference and engaged in exports of rice from Taiwan. Such trade exchange was allowed by the Qing government because the merchants’ vessels helped undertake the official duty of “Tai-yun”. The circulation structure of “Tai-yun” was dependent on commercial vesselss for rice transport while subjected to restrictions under government policies concerning official ports, navigation routes and vessels allowed. After the end of Lin Shuangwen Rebellion, the rice price of southern Taiwan rose (1788-1789 A.D.), and exceeded that of Quan-zhou Prefecture, meaning diminished profits for rice exports from southern Taiwan. The relatively lower rice price of northern Taiwan drove merchants to export rice from illegal ports in the central and northern Taiwan. At the same time, to shun their commitment in “Tai-yun”, rice merchants began to transport rice in fishing vessels and small boats, which were not allowed to cross the Taiwan Strait. Such intentional evasion of “Tai-yun” persisted throughout the reign of Emperor Jiaqing (1796-1819 A.D.), during which the price of rice all over Taiwan dropped. Profits from rice trade continued to decline in the mid 1830s when the difference in rice price between Taiwan and Quan-zhou Prefecture further narrowed. Hence, reduction in profits led to fewer merchant vessels visiting official ports for rice trade, thus affecting “Tai-yun” declined by the decrease of commercial fleets. Consequently, the circulation structure of “Taiyun” disintegrated during the first half of the 19th .