Six of the men, or 16 per cent, were found to have the virus SARS-CoV-2, which causes coronavirus, in their sperm sample. Two of them had already recovered from the illness.
It suggests the bug can persist much longer in the testes than in other areas of the body and could be spread during sex, according to scientists.
Researcher Dr Shixi Zhang, from the Shangqiu Municipal Hospital wrote in the journal JAMA Network Open that "the survival of SARS-CoV-2 in a recovering patient's semen maintains the likelihood to infect others".
Professor of andrology at Sheffield University Allan Pacey said the findings open up the possibility of sexual transmission.
"It shows that RNA for the virus responsible for Covid-19 can be detected in the semen of a proportion of 16 per cent of men with a confirmed infection.
"This opens up the possibility that one route of infection may be through sexual contact, although this was not confirmed in the paper.
"However, we should not be surprised if the virus which causes Covid-19 is found in the semen of some men since this is been shown with many other viruses such as Ebola and Zika."
Others said that the study raised some "important questions".
Edinburgh University's Professor Richard Sharpe said: "It found a minority of men who have had Covid-19 infection diagnosed in a hospital, also exhibit the presence of Covid-19 virus in their semen.
"This included men in the active stage of infection but also a couple of men who were in the clinical stages of recovery from Covid-19.
"This finding raises the possibility that Covid-19 might also be transmissible via semen and thus via sexual contact, perhaps including during the recovery phase."
