Crude oil takes the fundamental part of the industry, and is the one of the most used resources in the world. Many places use crude oil. Republic of Korea is a major importer of crude oil. If the crude oil cannot be imported, it will pose a great threat to domestic consumption and foreign export of petrol chemical products. Therefore, it is essential to import liquid cargoes such as crude oil. Existing research mainly confirmed the competitive relationship between container ports. There would be a possible relationship between the national and regional port dealing with liquid cargoes. In order to differentiate our study, we selected Ulsan port, Daesan port, and Yeosu Gwangyang port to confirm competition relationship between liquid cargo ports. In this study, A Vector Auto Regressive model using time series variables was used. A Unit Root Test was performed. The relationship between the ports was confirmed through the Toda Yamamoto Causality Test.