Liu Zhang was Liu Bang's grandson, but Liu Bang had sons (Liu Heng and Liu Chang) at that time. According to the ancient concept of inheritance, it is arranged according to the distance of blood. If you don't have children, the grandson of the person you are looking for is very talented and can take on a big job. For example, Liu Ao, the emperor of the Han Dynasty, became emperor after his death because he had no children. After the rebellion of the Lu Dynasty was put down, Minister Zhou Bo and Chen Ping discussed and elected the emperor. On the pretence, Liu Ze suggested to Liu Xiang to go to Chang 'an to lobby his ministers to make Liu Xiang the son of heaven, but when he arrived in Chang 'an, he said: Liu Xiang's uncle is not a kind person. If Liu Xiang is established, it will mean that the history of "serving the country with Lu" will repeat itself. Ministers are very afraid of the reappearance of consorts. After discussion, ministers agreed that acting king Liu Heng was suitable to inherit the throne. Because the little emperor and the little prince who are now in the mercy position are not Hui Di's own (this is controversial), Dai Wang is the son of Emperor Gaozu, who is generous and kind, and his mother Bo Shi is also very kind, so there will be no self-reliance phenomenon. The most crucial point is that the generation of kings is the oldest and there is no controversy in the country. So, frequency, Chen Ping and others personally went to Chang 'an to meet Wang Ren, who was the seat of mercy. In September, Liu Heng, the acting king, and his party went to Chang 'an from generation to generation. With the support of his ministers, they proclaimed themselves Emperor of Chinese. Liu Zhang first made great contributions by personally beheading the Prime Minister Lu Chan, and was later awarded a salary of 2,000 households by Emperor Wen of the Han Dynasty. In BC 178 (the second year of Emperor Xiaowen), Liu Zhang became King of Chengyang from Zhu Xu and Houjin, and established Chengyang Kingdom. At the beginning, because of his meritorious service in pacifying Lu, Emperor Wen of Han once named him Qiu. But later, Emperor Wendi learned that Liu Zhang intended to hold his brother Liu Xiang, the king of Qi, as the throne, but he was not happy, and only named him King Chengyang.