The Chinese athlete did not threaten the stunning 46.80 seconds mark he set with the lead-off swim in Sunday's relay at the World Championships but 47.53 was enough to secure his first individual world gold at the Aspire Dome pool.
He had to fight for it, though, with Italian runner-up Alessandro Miressi and Hungary's bronze medallist Nandor Nemeth threatening to upset the Chinese favourite in a furious finish.
"I was a bit nervous because this is my first individual final at the World Championships," Pan told reporters.
"My time was just so-so. I tried my best but my level was not that strong. I know it's only the beginning. Let's meet in Paris."
Pan was strong favourite for the title but Canadian Finlay Knox's 200 metres individual medley title was something of a surprise.
The United States' Fukuoka runner-up Carson Foster had bigger claims but Knox took him down from lane seven in the final freestyle leg to win in 1:56.64.
Italy's Alberto Razzetti claimed bronze.
"Historically, I'm pretty slow with backstroke (but) the last 50 everyone knows you just have to dig deep and go for it," said Knox.
In a modest field lacking all of the Fukuoka medallists, Briton Laura Stephens won the women's 200m butterfly title in 2:07.35, pipping Denmark's Helena Bach by less than a tenth of a second.
Bosnia's 18-year-old Lana Pudar took bronze and enjoyed the biggest cheers of the night from a rowdy pocket of Bosnian fans.
CURZAN WINS AGAIN
American Claire Curzan continued her fruitful campaign by winning the non-Olympic 50m breaststroke in 27.43 seconds, pipping Australian surprise package Iona Anderson by 0.02 seconds.
Having missed out on a spot in the United States' World Championships team to Fukuoka last July, Curzan now has four medals, including golds in the 100m backstroke and mixed medley relay.
Olympic silver medallist Siobhan Haughey eased into the women's 100m freestyle final, a day after becoming Hong Kong's first swimming world champion with her 200m win.
Haughey, runner-up behind Mollie O'Callaghan in the 100m at last year's event in Fukuoka, qualified second behind the Netherlands' Marrit Steenbergen.
World record holder Sarah Sjostrom was entered in the 100m but did not swim. The Swedish veteran told home media this month she is not planning to compete in the event at Paris.
With world champion Tatjana Schoenmaker skipping Doha, American Kate Douglass is on track for a second title at the meet, qualifying second for the 200m breaststroke final on Friday.
The Netherlands' Tes Schouten is top seed with a time of 2:21.50.
Douglass, who won the 200m individual medley this week, was runner-up to South African Schoenmaker in the 200m breaststroke last year.
Finland's Olympic bronze medallist Matti Mattsson qualified fourth for the men's 200 breaststroke final on Friday, with American Jake Foster top seed with a time of 2:08.78.
