Why did the Han government allow the southern Xiongnu to immigrate into the prefectures on the fringe of the Han border? In this paper we discuss only the financial reasons of the Han empire's policy on this issue. The nomad economy of the Xiongnu was not self-sufficient. They depended on the supply of the agricultural society of the Han empire in several ways. First, the Xiongnu raided the Han border prefectures and took the ration and other goods. Second, the Han emperor offered consorts to the Xiongnu chieftains when the latter surrendered and were recognized as the subject of the former. Third, the Han emperor made payment of cash and goods to the Xiongnu when the latter was strong and the former wanted peace. The Han government had to pay the Xiongnu whatever they asked to maintain peaceful relations. The only way the Han government avoided payment to the Xiongnu was to wage war, defeat the Xiongnu and chase them far away from the border. But the cost of war deemed too expensive. In the beginning of the Eastern Han, the southern Xiongnu surrendered to the Han emperor. The Han government settled them in the regions inside the border, and kept them under surveillance. The government considered that this was the best way to handle the matter financially, though the emperor still gave a large sum of valuable gifts annually to the Chief of the southern Xiongnu, and provided the tribesmen with economic assistance in their difficult times.