On 29 August 2015, Su raced with his teammates Mo Youxue, Xie Zhenye and Zhang Peimeng in the 4 × 100 metres relay. Running the third leg, Su aided his team to a third-place finish in the heats, qualifying them for the final with a then Asian record time of 37.92 seconds. In the final, the Chinese team crossed the line in third behind the United States and Jamaica in 38.01 seconds, giving them a Bronze Medal finish. However, subsequent disqualification of the United States due to improper baton exchange meant that the Chinese team were promoted to a Silver medal finish in the Bird's Nest Stadium; with their Bronze being awarded to Canada.