淝水之戰
Murong Wei was relocated with most of his clan to the Former Qin capital Chang'an. Fu Jiān created him the Marquess of Xinxing and made him a general. In 378, he participated in the campaign of Fu Jiān's son Fu Pi in sieging Jin's important border city Xiangyang. In 383, he also participated in Fu Jiān's massive campaign against Jin, through which Fu Jiān hoped to destroy Jin finally and unite China. After the defeat at the Battle of Fei River, however, Fu Jiān's forces collapsed, and, after Murong Chui, at that time, declined to start an uprising to reestablish Yan, Murong De tried to persuade Murong Wei to do so, but Murong Wei declined as well and accompanied Fu Jiān back to Chang'an.