Crowd estimates varied, but one police officer said as many as 50,000 people, most of them Muslim, had gathered on Wednesday in a fairground in central New Delhi - ordinarily used for political rallies - ahead of Bush's arrival later during the day.
Among the speakers was Raj Babbar, a Hindu politician and actor, who said: "Whether Hindu or Muslim, the people of India have gathered here to show our anger. We have only one message - killer Bush go home."
While Bush remains more popular in India than he is in many other countries, many in India object to US policies, especially the invasions of Iraq and Afghanistan.
Police, some of them armed with rifles, were heavily deployed around the fairground, but as the rally grew, protesters charged a stage where about 200 Muslim leaders were waiting to speak, knocking over television cameras.
Police put the number of protesters at about 50,000 but organisers said 300,000 people had joined the demonstration.
President Bush will arrive on a
three-day visit to India
A smaller protest was held at the historic 17th-century Jama Masjid mosque in Old Delhi, witnesses said.
"We do not want Bush here as he is the world's biggest terrorist. He has no place in the land of (freedom hero Mahatma) Gandhi," said Jamiat Ulama-i-Hind spokesman Abdul Hameed Naumani.
The protesters shouted "Bush murdabad" (Down with Bush), "Bush vaapas jao" (Bush, go back) and waved black and white flags.
Left-wing parties and workers' organisations were also preparing for similar protests on Thursday.