A Chinese mother whose only son is on life support in a Melbourne hospital says she is overjoyed to be given an emergency visa and says she "just wants to see him".

Xing Lan Ren's son, 22-year-old Xiao Li, has been in the Royal Melbourne Hospital in a critical condition since his car collided with a truck on January 27 between Melbourne and his home in Sale, East Gippsland. He was declared brain dead on Monday.

Xiao Li came to Australia last May on a working-holiday visa.

On Friday afternoon, acting Immigration Minister Alan Tudge said the government had granted Ms Ren a visa in what was its first exemption to the blanket ban on foreign nationals coming from China due to "overwhelming compassionate and other considerations".

Mr Tudge said government officials were now liaising with Ms Ren to bring her to Australia as soon as possible, with doctors expected to keep Mr Li's life support on until she arrives. A friend of Mr Li said she is planning to arrive in Melbourne on Sunday morning.