The contest has thrust the small city of Nelspruit into the spotlight, with foreign television crews planning to cover the event.
One of the pageant's organisers, Markus Buitendach, said homophobes from surrounding towns were threatening to hold a sit-in at the Nelspruit civic centre which is to host the event.
The threats follow condemnation by a local protestant minister in Nelspruit - a place which has made a rapid transformation from agricultural town to capital of Mpumalanga province.
"We find it offensive, and this community in Nelspruit has strong Christian values," said Rev Thinus Taute.
Judges will be voting for Miss Gay South Africa from a shortlist of 10 finalists chosen from regional heats all over the country.
The organisers hope this first Ms Gay South Africa pageant will promote greater tolerance beyond this country's borders.
Homosexuality in Uganda is illegal, while President Robert Mugabe of Zimbabwe says gay people are no better than dogs.
"That will be Ms Gay South Africa's purpose in her year of reign - supporting the gay people of Zimbabwe in their struggle. She'll be doing fundraisings and public speaking on their behalf," Mr Buitendach said.
Although Nelspruit itself may harbour conservative attitudes, South Africa is the only country in the continent where an event like the pageant could take place.
The former land of apartheid now has one of the most liberal constitutions in the world. Gay men and women cannot be discriminated against, and can marry and can adopt children.