Ainslie has previously struggled at the beginning of Olympic Games, but flourished on the home waters of the south coast this afternoon.
He finished the day with two second places behind Denmark's Jonas Hogh-Christensen.
'It was a good day,' he said. 'They were tough conditions out there, especially on the Nothe Course [in the first race].
'There was very, very shifty winds but it was a good start. It was ok, but there is a long way to go.'
The opening races both finished with the same top three of Croatia's Ivan Kljakovic Gaspic then Ainslie in second and Hogh-Christensen.
The Dane was pleased with his performance but keen to stress this it is only the beginning of the regatta.
'It was a great day, but Ben and Ivan are close behind and we're very early in the regatta,' Hogh-Christensen said. 'I need to keep cool, take it one day at a time and focus on tomorrow.'
The other men's class to start on Day 2 of the Games was the Star and saw British pair Iain Percy and Andrew Simpson recover from a difficult start to end the day in fifth overall.
The reigning Star gold medallists endured a poor first race in which they ended 11th, but responded superbly to end the day's final race in the top two – behind race winners Robert Scheidt and Bruno Prada from Brazil.