Left-handed opener Smith smashed an attractive 65-ball 91 as the world number one team made short shrift of Scotland who were left with the consolation of having reached their highest World Cup score of 186-8.
The win, wrapped up in the 24th over, may have looked like easy for the Proteas, but they failed to bowl out Scotland inside 50 overs which could be a worry for them in the second round.
Smith went on the attack from the outset, reaching his fifty off just 36 balls with ten boundaries.
His previous best World Cup score of 67 was made against the Netherlands last week.
Fellow opener AB de Villiers, who scored 62, made up for his nought against the Netherlands by hitting two consecutive sixes off left-armer spinner Glenn Rogers before holing out in the same over. He also hit nine fours.
Ashwell Prince, promoted to number three to get practice, seemed to get distracted by a 25-minute rain break and was caught for 21.
After the break, Smith, in a hurry to reach his hundred, also lost his wicket to off-spinner Majid Haq who finished with 2-43.
Smith hit 13 boundaries and a six.
Earlier, the South Africa skipper put Scotland in to give his bowlers a chance before their crunch match against Australia on March 24.
Andrew Hall (3-48) and fellow paceman Charl Langeveldt (2-48) enjoyed a good work out.
Dougie Brown, who top-scored with 45 not out, and John Blain (23) gave the Scots' total some respectability with a 50-run stand for the seventh wicket. Brown hit three boundaries during his 64-ball knock.
Stand-in Scotland captain Ryan Watson made 31.
Watson, replacing regular captain Craig Wright who had gone home to attend a family funeral, hit four boundaries during his 50-ball knock.
Openers Fraser Watson (24) and Majid Haq (13) gave Scotland a confident start of 31 before both were removed in the space of five overs.
Hall struck twice to remove Haq and Gavin Hamilton (four) to stop Scotland's progress, while Langeveldt got rid of Watts.
Scotland, whose previous highest score in the World Cup was 181 against Australia at Worcester in 1999, batted with resolve to complete their quota of 50 overs.
Paceman Makhaya Ntini, who replaced fellow paceman Andre Nel as the only change from South Africa's 221-run win over the Netherlands in their first match, failed to get a wicket in his nine overs before leaving the field with cramps.
Ntini missed the first match after joining the team late due to the birth of his daughter back home.
The two sides observed a minute's silence in memory of the late Pakistan coach Bob Woolmer before the start of the match.
They also wore black arm bands to mourn Woolmer's death of Sunday.
Woolmer, a former England batsman, also coached South Africa from 1994 to 1999.