Holding tricolours, thousands of his supporters raised slogans as Ramdev sat on the dais with patriotic music playing in the background.
The yoga guru had arrived in the capital on Thursday morning from Gujarat where he had been meditating since Monday at Vallabhbhai Patel's memorial.
Before coming to Ramlila Maidan, Ramdev paid tributes to Mahatma Gandhi and Bhagat Singh at Rajghat and Shaheedi Park.
Delhi Police have given the organisers permission to host 30,000 people a day and hold the agitation there till Aug 30.
A similar agitation at the same venue by Ramdev a year ago had ended in a police crackdown and the death of a woman.