Due to the low inlet temperature, the heat loss of liquid carbon dioxide is negative. Due to the influence of the Joule Thomson effect, the temperature will continue to decrease, and the amplitude of primary heat loss will also increase with the increase of transportation distance. In contrast, in the supercritical state, due to the high inlet temperature, the heat loss is positive, meaning that it releases heat to the outside world. When the pipeline transportation distance exceeds 400km, the heat loss reaches a stable state, while in the gaseous state, When the conveying length is less than 47.5km, due to the high temperature, the heat loss is positive. However, as the distance increases, the pressure further decreases. Due to the prominent Joule Thomson effect, the medium temperature will drop below the ambient temperature, resulting in a negative heat loss and manifested as heat absorption from the environment