In 361, Emperor Mu died without a son. Emperor Mu's mother Empress Dowager Chu thus ordered that Sima Pi be made emperor, and he took the throne as Emperor Ai, at age 20. He created his wife Princess Wang as empress, and his brother Sima Yi, who previously carried the title the Prince of Donghai, as the Prince of Langya. Since he was an adult, Empress Dowager Chu did not serve as regent for him, and he honored his mother Consort Zhou as Consort Dowager () in 362, but with supplies and ceremonies similar to the empress dowager. However, the decision-making process was largely in the hands of the general Huan Wen and Emperor Ai's granduncle Sima Yu the Prince of Kuaiji.