Britain were leading after the first half when Ashley Jackson scored for the team in the 14th minute.
But two late strikes from Austin Smith and Jonathan Robinson gave South Africa 2-1 lead.
However, Britain were lucky to level the match as Jackson scored again in the last minutes of the game.
The riveting performance by the hosts in their opening London 2012 Olympics match was missing – but they held their lead at half-time.
South Africa weren’t happy with the decision of the second British goal and appealed to the umpire but they had already used their team referral earlier in the game.
Britain forced a penalty corner in the dying moments but couldn’t convert it.