Fan said his working hours are typically from 9 am to 9 pm, with an hour break for lunch at noon.
He worked on Tuesday, though it was May Day, within the three-day national holiday from April 29 to May 1.
"For people like us, working on weekends or holidays is so common, because most of our clients have time to look for apartments (to rent or buy) on non-workdays," he said, adding that his company pays him triple wages for overtime.
The poll did not offer data on how many of the people who work overtime receive their legally mandated extra pay.
Feng Nan, 27, who works for a public relations company in Beijing, said sometimes people feel that they have to work extra hours to impress their bosses.
"Our supervisor admires the busy bees and is one himself, so how can I leave the office and go home if my supervisor is still at his desk," she said.
Feng Tongqing, a labor professor at the China Institute of Industrial Relations, said overworking is difficult to avoid in the service sector and manufacturing industry in developing economies such as China.
The phenomenon becomes worse when labor unions are too weak to fight for workers' rights, such as guaranteeing reasonable working hours and decent pay, he said on Tuesday.
Feng argued that the global economic downturn also forced Chinese workers to work harder than before.
"Many small or medium-sized companies have to fight more fiercely for their share of the domestic market. These companies' owners transfer the survival pressure to their employees, who have to sweat more to keep their jobs secure," he said.
Guangzhou, in South China's Guangdong province, could be called the most tiring of the 28 cities surveyed.
First, it had the longest average workday, at just over nine hours. But 12 other cities, including Hangzhou and Shanghai, followed Guangzhou on the list of cities where the average workday was longer than eight hours.
Second, it topped the list of cities where workers get the shortest night's sleep, at seven hours and 12 minutes.
Beijing respondents on average spend an hour and 20 minutes commuting to work and back. Workers in five other cities, including Shanghai, also spend more than an hour commuting on workdays.
The poll also found that workers spend less than an hour a week on sports or fitness.