Su clocked 10.05 in second, while Xie Zhenye was third in 10.17 and Ujah fourth in 10.18.
"My expectations going in were that I knew I had it in me as long as I executed my race".
"It is just a start, I hope I can be better and better in the future, I have told my coach that I wanted to showcase my best form in Eugene, even just a little progress", he added.
Su admitted the strong squad which featured Justin Gatlin would help him to run better.
Bahamian Olympic champion, Shaunae Miller-Uibo, powered home in the women's 200 metres, clocking one of the eight meet records of the day to win in 22.06 seconds. She went on to improve her mark to 66.85m in the third round and bowed out with a 66.26m to wrap up the victory, reports Xinhua news agency.
South Africa's Wenda Nell had to settle for fourth place on the women's 400m hurdles in a time of 55.63, well down on the winning time of 53.77 set by American Dalilah Muhammad, with Jamaican Janieve Russell (53.78) and Canada's Sage Watson (55.23) claiming the other podium places.
In his first 110m hurdles race this year, Jamaica's world and Olympic champion Omar McLeod edged Spaniard Orlando Ortega in a repeat of the Rio Games to win in 13.16 seconds.
Chinese world champion Gong Lijiao showed her class in women's shot put with 19.99m to win in front of the delighted home crowd.
The women's 3,000m steeplechase had some drama towards the end when Norah Jeruto slipped coming off the final barrier and fellow Kenyan Beatrice Chepkoech won in 9:07.27 minutes. Britain's Andrew Osagie was seventh in 1:46.36.
World silver medallist Steven Gardiner of Bahamas claimed another win as he broke the 400m meeting record with 43.99 ahead of Botswana's Isaac Makwala with 44.23, while USA's Olympic and world triple jump champion Christian Taylor was fifth in 45.24.
Kenya's world 1500m silver medallist Timothy Cheruyiot was a victor of the 1,500m in 3:31.48, a 2018 leading time, ahead of Ethiopia's Samuel Tefera, who set a personal best of 3:31.63.
Ethiopia's Birhanu Balew won the 5000m in 13:09.64 from USA's Paul Chelimo with 13:09.66.
Colombia's Olympic triple jump champion Caterine Ibarguen, who was unbeaten for nearly four years until losing at the 2016 Birmingham Diamond League meeting, maintained business as usual with victory in 14.80m, the farthest achieved so far this season.
Russia's Maria Lasitskene cleared a world-leading 1.97m to win the high jump, while France's Renaud Lavillenie won the pole vault on countback ahead of Poland's Piotr Lisek, as both athletes cleared 5.81m.