He told the BBC the region would declare its independence by the end of this week or the beginning of next week.
The announcement comes after Catalonia held a referendum on Sunday, which Madrid deemed as illegal.
This evening the King of Spain attacked the Catalonia independence referendum organisers for their “lack of loyalty to the Spanish government” in an unprecedented televised address to the nation.
The Madrid government has vowed to stop the north-eastern region from breaking away from Spain and has called the vote “illegal”.
At least 893 people and 33 police officers were reported to have been hurt on Sunday after police stormed polling stations to stop voters.
Mr Puigdemont said the EU can not look the other way after 900 people have been injured in the referendum crackdown.
According to the Catalonia government, 2.26million people took part in the poll, which is 42 per cent of the electorate.
A total of 90 per cent of people in Catalonia voted for independence.
The Spanish tennis player Rafael Nadal said: “I want to cry when I see a country where we have known how to co-exist and be a good example to the rest of the world get to a situation like this”.
Prime Minister of Spain Mariano Rajoy said the referendum “only served to cause serious harm to coexistence”.
The Scottish government has urged Boris Johnson, to ask the Spanish government to enter dialogue with the Catalans.