“Nobody can tell us where and when we, Catalans, can show our symbols,” said Jordi Sanchez, the president of the Catalan National Assembly, a pro-independence organisation which has in recent years organised massive demonstrations in favour of Catalonia's secession from Spain.
Some 300 volunteers from several pro-independence groups will give the flags to fans going into Barcelona's match on Wednesday at the Camp Nou and will ask them to display them.
European football's governing body fined Barca €40,000 ($44,000, £28,800) for the flags displayed during the European champions' 2-1 win over Bayer Leverkusen last month.
It was the second such sanction in a matter of months as Barca were fined €30,000 for the same reason after their Champions League final success against Juventus in Berlin in May.
Uefa argues the use of the flag violates its regulations, which prohibit “the use of gestures, words, objects or any other means to transmit any message that is not fit for a sports event, particularly messages that are of a political, ideological, religious, offensive or provocative nature”.
Barcelona president Josep Maria Bartomeu has threatened to drag Uefa through the courts for violating the club's fans' right to freedom of speech.
Catalans' longstanding demands for greater autonomy have intensified in recent years, in tandem with the country's economic crisis.
Home to 7.5 million people, Spain's richest region has its own widely spoken language and distinct culture.
Pro-independence parties won a majority of seats in the Catalan parliament in Barcelona for the first time in elections last month.
They are seeking to pass a resolution in the Catalan parliament in early November announcing the formal start of secession from Spain and the formation of a new republican state within 18 months.