He told activists: "We will stop the boats and we will detain and deport those who illegally break into our country."
He said this was what "nearly every normal country around the rest of the world does".
"You cannot come here illegally and stay. We will stop the boats within two weeks of winning government," he added.
In plans announced last month, Reform UK suggested it would be prepared to deport 600,000 migrants over five years if it won power at the next general election.
Farage said his party would bar anyone who came to the UK on a small boat from claiming asylum and make £2bn available to offer payments or aid to countries like Afghanistan to take back migrants.
Key to the plan is the passage of a new law called the Illegal Migration (Mass Deportation) Bill.
Reform UK said the bill would create a legal duty for the home secretary to remove illegal migrants, and ban anyone who had been deported from re-entering the UK for life.
The bill would also "disapply" international treaties like the Refugee Convention, a 1951 treaty that prevents signatory countries like the UK from returning refugees to countries where they face serious threats to their life or freedom.