The crowd outside Guangzhou station swelled to nearly 100,000 at its peak on Monday night, police said.
Central China has experienced some of its coldest weather in years.
The rare snow has coincided with the run-up to Chinese New Year - where hundreds of millions of migrant workers travel home to see their families.
Many trains from north and central China were delayed by the snow - leaving passengers in the south stranded with no transport.
More than 50,000 people still remained stuck outside Guangzhou railway station on Tuesday, state media said.
Local police said 5,200 officers had been deployed to maintain order.
They urged passengers to check their train details online and avoid "blindly heading to the station to wait for trains", saying this would exacerbate the overcrowding.
Officials estimate nearly three billion trips will take place over the holiday season, in what is considered the world's biggest annual human migration.
Meanwhile, traffic jams had led to more than 400 people in Guangzhou missing their flights, Xinhua news agency reported.
Heavy snow has disrupted public transport in southern China, stranding tens of thousands of people outside a rail station, police say.