Nadal, currently ranked eighth in the world, started as strongly as many expected against his unfancied opponent in Beijing.
However, an early break of serve was immediately broken back by Di, who then held serve well to make it 3-3.
Di pushed for an opening towards claiming the first set but Nadal's quality shone through and he snatched serve a second time before taking a 1-0 lead in sets.
Wimbledon order of play, Day 4 - When are Swiatek, Nadal and Boulter playing?
The second set was intriguingly error-strewn and only one game in that set was won on serve.
But though Nadal was 3-1 and 4-2 down at stages, he broke twice more from there to take it in straight sets in a far less comfortable manner than he probably hoped.
"The last three games of the match I was playing better. I hit some good forehands down the line and that's why I finished well,' Nadal said afterwards.
“(I’m) practising well, the level of tennis going to be there sooner or later. I am working a lot to make that happen. I think I'm closer to that.
There were no such problems for top seed Novak Djokovic, who dispatched Simone Bolelli 6-1 6-1 to continue his unbeaten record in the event.
The Serbian has won all 25 of his matches in Beijing, a run that stretches back to 2009, and is looking to add a sixth title to his collection this week.
Djokovic will play Australian qualifier John Millman in the second round, while Nadal faces Canada's Vasek Pospisil.
'It'd be very unique' - Djokovic on reunion with Federer, Nadal and Murray
Wilander compares Djokovic's defensive skill to Federer after 'flawless' display