Aung San Suu Kyi, a former political prisoner, entered parliament last year and was chosen to remain as NLD chairwoman unanimously by the party's 120-member central committee, a source told the AFP.
She is one of four women on the NLD's 15-member executive, a BBC report from Yangon said.
"For the benefit of the country we should unite and get along," she told the assembly of 900 delegates, chosen to attend the party congress, which began on Friday.
"This congress is about choosing the right leaders who will serve both the future of our organization and our country," she said.
Aung San Suu Kyi, daughter of independence hero General Aung San, was placed under house arrest by the country's ruling military junta in 1989. She was released after an election in 2010, from which she was barred. She was sworn into the parliament weeks after the NLD's landslide victory in the by-elections last April.
Her party is planning to bring about youth-oriented reforms amid differences of opinion between the party’s senior leadership and younger members.