Beijing says it faces a serious threat from Islamist militants and separatists in Xinjiang and has rejected accusations of mistreatment.
Asked about the Pakistani businessmen on Tuesday, Geng Shuang, a spokesman for the Foreign Ministry, told a regular news briefing that he was not aware of the situation.
Muslim majority nations have mostly remained silent over the situation in Xinjiang.
Last month's election of cricketing legend and firebrand nationalist Imran Khan as Pakistan's prime minister has fed the expectations of many for him to deliver on promises to create jobs, build an Islamic welfare state and restore the country's image abroad.
Mian Shahid Ilyas, a businessman in Lahore who has been collecting details of cases and seeking government support, said he was optimistic the new government would help.
Pakistan's foreign ministry in Islamabad did not reply to questions from Reuters on the Uighur spouses.
"A lot of people get married like us. It's no problem. But in 2017 they start to seal everything off in Xinjiang," Ilyas, who said his Chinese Uighur wife, a citizen of China, had been detained since April 2017, told Reuters by telephone.
Ilyas said he had confirmed details of 38 cases but believed there were more than 300 similar cases of Pakistani husbands whose wives and children, most of them Uighurs, had been stuck in Xinjiang for more than a year, in camps or confined to homes.
The handful of businessmen, including Baig, is travelling to China in groups of twos and threes, to avoid raising suspicion, parking themselves at the embassy to make their case, he said.
"This is China's big mistake," said Ilyas. "Before people did not know how they treated Muslims. Now, everyone knows."