Zhao Xintong first drew international attention in June 2012 at the Zhangjiagang Open defeating high ranking players Xiao Guodong and Yu Delu to reach the last 16 of the tournament where he narrowly lost 4–3 to Stephen Lee. Zhao would build on this success by reaching the second round of Asian Tour Events the Yixing Open and Zhengzhou Open.
As a wildcard entrant he defeated former World Champion Ken Doherty in the International Championship to reach the last 32 of a ranking event for the first time, again narrowly losing in a final frame decider 6–5 to Matthew Stevens. Having also earned he way to the last 32 of the World Open and China Open, Zhao started gaining the reputation of the Wildcard Menace.
In 2013, at the International Championship, he beat six-time World Champion Steve Davis 6–1 who later commented: "This boy was astonishingly good and better than anybody I have ever seen at that age - and that includes Ronnie O'Sullivan." He went on to reach the third round of the competition before losing 6–2 to Marco Fu, however he would go on to avenge this loss by defeating Fu in the first round of the 2014 Shanghai Masters.[deprecated source] Zhao entered the World Amateur Championship in late 2013 reaching the final, however he lost to his fellow countryman Zhou Yuelong 8–4 and thus missed out on a chance to join the world snooker main tour for the 2014/2015 season.
Zhao entered several events in an attempt to qualify for the 2015/2016 season. He was narrowly defeated in the first round of the ACBS Asian Snooker Championship. Xintong won three games in the first event of Q School before losing 4–3 to Alexander Ursenbacher in the penultimate round. In the second event Zhao got extremely close to qualifying for the main tour managing to reach the final round before losing before losing 4–3 to Duane Jones in a black ball finish in the deciding frame.
Zhao's high Q School Order of Merit ranking gave him entry as a top up player to many events in the 2015/2016 season. He whitewashed Stuart Carrington 6–0 to qualify for the International Championship and, despite losing 6–2 to John Higgins in the first round, his effort of 142 won the high break prize for the event. Zhao made his first appearance at the UK Championship, German Masters and Welsh Open, but was knocked out in the opening round of each. He lost in the final of the 2015 IBSF World Snooker Championship 8–6 to Pankaj Advani. It meant that Zhao won a two-year card for the main tour after Advani declined the invitation.
After whitewashing Wang Yuchen 4–0 at the English Open, Zhao met Ronnie O'Sullivan in the second round. Breaks of 130, 107 and 80 saw him lead 3–2, but he missed chances to take the win and was defeated 4–3. O'Sullivan said afterwards that Zhao's attacking style of play had reminded him of Stephen Hendry when he was a similar age. He qualified for the German Masters by beating Li Hang 5–3 and John Higgins 5–1 and a 5–0 thrashing of Akani Songsermsawad saw Zhao reach the last 16 of a ranking event for the first time. He held a narrow 4–3 advantage over Ali Carter, but lost the last two frames. Zhao was also edged out in the third round Gibraltar Open 4–3 by Mark Williams.
He dropped off the tour at the end of the 2017/18 season but entered Q School in a bid to win back his place. He subsequently won back his place by beating Dechawat Poomjaeng in the second Event final of Q School.