Batting first, after winning the toss at the M A Chidambaram Stadium, he Aussies were all out for 272 in 47.2 overs.
In reply, the South Africans was bowled out for 164 in only 37.1 overs.
Cameron Boyce (3-48) and Ashton Agar (3-41) picked up three wickets each. They were ably supported by pacer Nathan Coulter-Nile, who finished with economical figures of 2 for 8 from seven overs, as the Australians registered yet another big victory.
The Aussies have won all their matches en route Friday’s title clash.
Wade smashed his way to 130 off barely 106 balls to lay the foundation for the Australians. The wicketkeeper-batsman, whose knock included nine fours and seven sixes, was well-supported by Peter Handscomb, who scored a 62-ball 52, including three boundaries.
He was involved in three fifty partnerships with Joe Burns (11), Chris Lynn (29) and Handscomb during his stay in the middle.
Sean Abbott scored a 24-ball 23, inclusive of two fours.
Captain Dean Elgar was the South Africans’ top-scorer with an 85-ball 64, including six boundaries, while Khaya Zondo scored 47 off 50 deliveries.
Left-arm pacer Lonwabo Tsotsobe was the most successful Proteas bowler, returning figures of 3 for 50 in nine overs.
"Good to win four out of four, but it all comes down to the final on Friday and we'll be up for that, ready to go,” said Wade after the match.
"In any one-day game you want to be batting 50 overs, so myself, should probably have batted a little deeper there, Peter Handscomb through to 50 overs."
Scorecard
Australia ‘A’
T Head c Vilas b Viljoen 0
J Burns c Zondo b Tsotsobe 11
M Wade c Vilas b Elgar 130
C Lynn c Viljoen b B Hendricks 29
C Ferguson b Delport 4
P Handscomb c de Bruyn b Tsotsobe 52
A Agar b Elgar 6
S Abbott c Vilas b Tsotsobe 23
N Coulter-Nile c de Bruyn b Viljoen 1
C Boyce c de Bruyn b BE Hendricks 4
A Fekete not out 0
Extras: (B-1, LB-2, W-5, NB-4) 12
Total: (all out; 47.2 overs) 272
Fall of wickets: 1-0, 2-52, 3-110, 4-134, 5-202, 6-217, 7-257, 8-260, 9-272.
Bowling: GC Viljoen 8-1-57-2, LL Tsotsobe 9-1-50-3, B Hendricks 7.2-0-51-2, KA Maharaj 10-0-42-0, CS Delport 3-0-16-1, D Elgar 8-0-45-2, K Zondo 2-0-8-0.
South Africa ‘A’
R Hendricks run out (T Head) 10
C Delport c G Sandhu b Nathan Niles 12
T Bruyn b Nathan 0
D Elgar c A Fekete b A Agar 64
O Rameela c C Boyce b S Abbott 15
K Zondo b Boyce 47
D Vilas b C Boyce 1
K Maharaj c P Handscomb b C Boyce 1
H Viljoen c Handscomb b A Agar 0
B Hendricks c Coulter Niles b A Agar 0
L Tsotsobe not out 0
Extras:(B-4, LB-6, W-4) 14
Total: (all out, 37.1 overs) 164
Fall of wickets: 1-18, 2-18, 3-37, 4-84, 5-142, 6-145, 7-147.
Bowling: Andrew Fedket 5-0-20-0, Nathan Coulter Niles 7-1-8-2, Sean Abbott 6-0-22-1, Cameroon Boyce 9.1-0-48-3, Travis Head 2-0-15-0, Ashton Agar 8-0-41-3.
Image: Matthew Wade
Photograph: Scott Barbour/Getty Images
Focus on India 'A' captain Unmukt as tri-series kicks-off
Agar, Burns get call-up for Australia ODI series vs England
Mayank's ton sets up a convincing win for India A
Khawaja, Burns set up easy win for Australia 'A'
Tri series: With SA players recuperating, Tuesday's match postponed