The Spaniard's return to the summit for the first time since July 2011 was confirmed on Monday when the new ranking list was published.
Nadal had secured his return to the top by reaching the final of the China Open, although he went on to lose that match to the man he has replaced as number one, Novak Djokovic.
It was his 13th final from 14 tournaments played since returning to the ATP World Tour in February following a seven-month injury lay-off. He has won 10 titles in that time, including the French and US Opens.
The one thing left to do is to finish the year in top spot, something Nadal achieved in 2008 and 2010.
Due to his absence from the tour this time last year due to a knee problem, Nadal has no more points to defend on the rolling 12-month ranking system this season so it is widely expected he will achieve that aim. However, it is not certain and Djokovic could yet finish at the summit for the third year in a row.
"[It] will be a great finish [to] the season if I am able to finish the season [at] the No. 1 spot," Nadal said in Beijing.
"For that, I am sure I need to win more matches if I want to be there."
Nadal added he would not be celebrating his achievement just yet.
"Celebrations are for the end of the season, not before," he said. "[It] is not my time for celebrations, it's time [to] keep being focused. The season is not over, my work is not over."
Meanwhile, Djokovic has not thrown in the towel in the race to be year-end number one just yet.
He said: "I have some room to get points here and there, but generally I just want to keep on playing well."
Both men are in action again this week at the Shanghai Rolex Masters, while they are also scheduled to appear at the Paris Masters and the ATP World Tour Finals in London before the end of the season.
Nadal is also due to compete in Basel later this month.
Andy Murray, currently out injured after undergoing back surgery, remains third in the ranking list but is likely to lose that position to David Ferrer next Monday.
Juan Martin Del Potro is up to fifth following his victory in the Japan Open, meaning Roger Federer slips to seventh.