Dealers have been able buy and sell the horns of South African rhinos legally inside the country since a court lifted a moratorium on domestic trade last year - though a global U.N. ban means none of it can be exported.
The Private Rhino Owners Association (PROA) said its new trading system would help people know they were buying horn taken from rhinos in South Africa legally and humanely.
"Every rhino horn offered for sale ... must possess a DNA certificate. Genetic profiling is the key control in establishing the provenance of every rhino horn on offer. By this mechanism no 'blood' horn is able to enter the market."
Campaigners fought for the global ban as poachers slaughtered rhinos across the continent, pushing some regional varieties to extinction. Five percent of South Africa's rhino population were killed in 2017, amid a recent surge in poaching.
But ranchers point to the fact that the horn can also be cut from a tranquilised animal and allowed to grow back.
PROA said its website, www.rhta.co.za, would "provide a managed, efficient platform from which genuine buyers and sellers can trade in 'clean', humanely acquired rhino horn."
The main demand for horn comes from Vietnam and other Asian countries where rhino horn is a coveted ingredient in traditional medicines.
The PROA estimates its members have around 6 tonnes of rhino horn in storage and reckons the state has a stockpile 25 tonnes - some of it seized in crackdowns on poaching. The combined total could fetch $2 billion by some estimates.
Conservationists have expressed concerns that domestic buyers could launder illicit supplies. Advocates of the legal trade say if the global ban was lifted then licit supplies could flow to Asia and potentially stem the poaching.
South Africa has more than 80 percent of the world's estimated 25,000 rhinoceroses. Rhino poaching rates in South Africa surged from 83 in 2008 to a record 1,215 in 2014.
More than 7,000 rhinos or around a third of the national herd are in private hands in South Africa, according to the PROA. Ownership of wild game there is legal.
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