The world number one, looking to lift the Suzanne Lenglen Cup for the third time in four years, started strongly before briefly struggling on Court Philippe Chatrier.
With several sponsors' seats empty in the middle of the afternoon, the Pole picked herself up quickly to end Liu's campaign in brutal fashion.
"It's not easy when you play with the wind and change sides to play against it. I'm happy I raised my level in the second set," said Swiatek, who turned 22 on Wednesday.
"Patience is important, especially on clay."
Swiatek raced to a 3-0 lead on a sunbathed Court Philippe Chatrier but she looked too much in a hurry and Liu pulled one of two breaks back as the Pole briefly lost her focus.
Liu levelled for 3-3 but dropped serve again as Swiatek bagged the opening set.
She did not look back, ending her opponent's ordeal on the second match point with a backhand winner down the line.
DAY SESSIONS
Swiatek next faces China's Wang Xinyu, and there is a chance that she will continue to play during the day as organisers have scheduled men's matches in all five night sessions so far.
While she advocates that women should get more exposure, Swiatek is personally happy that she does not have to play under the lights in Paris.
"Obviously it would be nice if we had women's matches as well," she told a press conference.
"But, as I said, I'm not kind of helping that because I always requested a day session match. There are players who like the hype and the energy, and maybe playing during the night because also of the conditions.
"But for me, it's more comfortable to just have the normal day/night rhythm. So in terms of regeneration, recovery, and just kind of being in a good rhythm and also keeping a better mindset through the end of the tournament, I think it's more healthy for me to play day sessions."
Swiatek, however, will not complain if French Open organisers ask her to play at night.
"If there is a pretty big request, I always kind of adjust," she said.
Last year, only one of the 10 night sessions, which are exclusively broadcast by Amazon Prime Video in France, featured women, with tournament director Amelie Mauresmo saying that men's matches were more appealing.
