Strikers Shivendra Singh (13th, 38th minutes), Dharamvir Singh (19th, 21st), Tushar Khandker (36th) and penalty corner specialist VR Raghunath (53rd) were on target for India.
The goal-scorers for South Africa last night were Austin Smith (17th, 69th), Tim Drummond (42nd), Ian Haley (48th) and Justin Ried Ross (67th).
Shivendra put India ahead in the 13th minute, scoring a field goal. South Africa -- who qualified for the London Olympics winning the last qualifier at Kakamigahara in Japan - equalised four minutes later through Smith, who converted a penalty stroke.
The South Africans then played a defensive game, but some sharp moves by the Indians helped forward Dharamvir score twice in the span of three minutes to help India led 3-1 at the half time.
The Men in Blue added two more after the lemon break, with field goals from Khandker (36th minute) and Shivendra (38th minute).
South Africa reduced the margin through Drummond and Haley in the 42nd and 48th minutes, respectively (5-3).
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India added one more in the 53rd minute through a penalty stroke by Raghunath, while Ross and Smith converted two penalty corners in the final minutes of the match to round off a 5-6 finish.
India will now play South Africa again on Wednesday.