The new president was speaking as the closing down ceremony of the country's first nuclear reactor, commissioned in 1978, on 19 June.
According to Korea.net, Moon said: "Elements that might pose any threat to the lives, safety and health of the people should be gotten rid of in the policies that we make.
"An era of clean energy that puts first the safety of the people is what our energy policies must pursue.
"The government will engage more actively in fostering clearer and safer sources of energy, such as new and renewable energies and liquefied natural gas."
Other reports said Moon would end the plans to build new nuclear reactors and would not extend the life spans of current nuclear sites.
The move offers an opportunity to the renewables industry, with nuclear power currently supply around a third of South Korea's electricity, according to the World Nuclear Organisation (WNO).
However, a complete phase out of nuclear could take 45 years, WNO said.
According to Windpower Intelligence, the research and data division of Windpower Monthly, South Korea has around 1GW of installed wind capacity, adding just 26MW so far this year, compared with 201MW in 2016.
It completed its first offshore wind project, the 30MW Tamra site, towards the end of 2016.