The Court of Arbitration for Sport (CAS) earlier accepted an appeal from the World Anti-Doping Agency (WADA) against a decision by swimming body FINA to clear Sun of wrongdoing for his conduct during the 2018 test.
CAS said the eight-year ban was imposed because Sun, 28, already had an earlier anti-doping rule violation against him from 2014.
Sun protested his innocence and said in a statement that he was angered by the decision.
