The Catalan government says more than 90 per cent of people who voted in the October 1 referendum voted in favour of independence from Spain.
Puigdemont is expected to address the regional Parliament on Tuesday, when Catalan leaders could declare independence, citing the results of a referendum that the national government and the courts had said was illegal and ordered suspended.
Meanwhile, the former leader of Catalonia, Artur Mas, told the Financial Times newspaper that the region was not yet ready for real independence - even though he believed it had won the right to break away.
"I am sad to see the state in which we find our country and the mediocrity of our government", said Marte Muro, 67, at the rally in Madrid, which drew several thousand people.
In 2014 we had the precedent of the Edinburgh agreement, two governments with diametrically opposed views on the question of independence nevertheless agreeing the process of letting the people decide.
"We will show these minoritarian secessionists that Spain is a modern country", Nobel Literature Prize victor Mario Vargas Llosa, a Peruvian writer who also holds Spanish citizenship, said in a speech at the end of the rally.
Some chanted "Don't be fooled, Catalonia is Spain" and called for Puigdemont to go to prison.
The massive pro-Spain march, which passed off without incident, ran under the slogan "For the restoration of seny" - the Catalan word for common sense or folk wisdom.
Barcelona police said 350,000 people participated, while march organisers Societat Civil Catalana said 930,000 people turned out.
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Other European Union countries have been anxiously watching how the unrest will play out.
Spain could use constitutional powers to suspend Catalonia's autonomy if it declares independence, Prime Minister Mariano Rajoy has warned.
Mr Rajoy assured Catalan leaders that there "is still time" to backtrack and avoid triggering a tough response from the central government in Madrid.
Kofi Annan, in his role as chairman of The Elders, a group of notable public figures formed in 2007 to promote peace, said: "The constitutional crisis that is unfolding in Spain calls for consultation and not confrontation". There is no alternative."Already battered by a corporate stampede to exit the region, the Catalan president is struggling to maintain support as the clock ticks down to a meeting on Tuesday that could trigger a split".
Thousands of people took to the streets and blocked roads across Catalonia yesterday amid strikes to protest against the police violence used during the weekend's divisive independence referendum.
With its own language and cultural traditions, demands for independence in Catalonia date back centuries but have surged during recent years of economic hardship.
The crisis is taking its toll and Puigdemont risks being cast adrift by the rest of Europe if he pushes ahead with plans based on a referendum a week ago that breached Spain's constitution. The Sunday rally may also give them pause, though pause for what is unclear since Spain is ruling out negotiations.
Reportedly, around 900 were injured on Sunday as the riot police raided polling stations and fired rubber bullets.
Dozens of protesters surrounded two Mossos vans and called the officers standing on guard in front of them "traitors".
The vote was not held according to official electoral standards as there were not regular voter lists, electoral commission or observers.