South Sudanese soldiers "will leave for the DRC as soon as possible," a spokesman for the South Sudan People's Defence Forces (SSPDF), Major General Lul Ruai Koang, said during a ceremony in the capital Juba.
The 750-strong battalion has been undergoing training for more than six months for their deployment, he added.
Fierce fighting in recent months between DRC troops and the M23 rebel group prompted the East African Community (EAC) bloc to deploy a joint regional force to quell the violence.
The EAC regional force is expected to include soldiers from Kenya, Burundi, Uganda and South Sudan. But its intended total size remains unclear.
Kenyan soldiers arrived in the country on November 12, with the Ugandan military later announcing that it would deploy 1,000 troops by the end of November.
At the Juba event on Wednesday, South Sudan President Salva Kiir instructed the troops to "keep order", urging them to "protect the civilians and their properties from any harm".
The ceremony came barely four months after thousands of fighters including former rebels loyal to Kiir and his rival, Vice President Riek Machar, were integrated into South Sudan's army -- a key condition of a peace deal to end the country's brutal civil war.
"I want to tell you that you are one army and no matter which division that you come from, now you are going as soldiers of South Sudan," Kiir said on Wednesday.