• As the officiant at the ceremony, the 54-year-old founder also urged the new couples to procreate, calling children a better investment that property.
• His message comes amid a dwindling birth rate in China and an increasing pressure on the country's slowing economy.
Jack Ma, founder and chairman of online marketplace Alibaba, has sparked criticism after advising his newlywed employees to have sex six times in six days.
Ma, also China's richest man, was speaking at his company's mass wedding which takes place every year on 'Ali Day' on May 10 at the company's headquarters in Hangzhou, east China.
'At work, we emphasize the spirit of 996. In life, we should follow 669,' Ma said. His remarks were a wordplay on the firm's controversial 996 work schedule, which expects staff to submit to 12-hour shifts between 9am and 9pm during a six-day week.
'What is 669? Six days, six times, with duration being the key,' Ma said to the 102 couples dressed in wedding dresses and suits at the ceremony. In Chinese, the word 'nine' is a homophone with the word for 'long'.
The quote was posted to Alibaba's official page on Weibo with a winking emoji, which drew widespread criticism from net users.
'Making a lewd joke in public and notoriously promoting it - are you being responsible to minors? Thumbs down this time,' one highly rated comment read.
'This is just revolting,' another comment said.
'Is this funny? Not one bit,' one person said.
'Who on earth would have the energy to 669 at home after 996 during work?' one user said.
As the officiant at the ceremony, the 54-year-old founder also urged the new couples to procreate, calling children a better investment that property.
'The first KPI of marriage is to have results. There must be products. What is the product? Have children,' Ma said.
'Marriage is not for the purpose of accumulating wealth, not for buying a house, not for buying a car, but for having a child together,' he added.
His message comes amid a dwindling birth rate in China and an increasing pressure on the country's slowing economy.
The number of babies born in 2018 fell by two million to 15.23 million - marking the lowest birth rate since 1961, despite Beijing relaxing its one-child policy in 2016.
However, many couples have opted not to have babies due to concerns including rising housing prices and access to high-quality education.
Ma, a former English teacher who co-founded Alibaba in 1999 and has become China's richest man, said he and early employees regularly worked long hours.
Defending the Chinese work practice of 996 last month, Ma called the long hours a 'huge blessing'.
'Many companies and many people don't have the opportunity to work 996. If you don't work 996 when you are young, when can you ever work 996?',' he said in remarks posted on the company's social media account.
'Let me ask everyone, if you don't put out more time and energy than others, how can you achieve the success you want?' he questioned. China's Labor Law stipulates that average work hours cannot exceed 40 hours a week.
MailOnline has reached out to Alibaba for comment.