With the government urging Venezuelans to celebrate his life, more than two million people have already filed past his body at a military academy.
His remains will be embalmed and placed on permanent display.
Later on Friday, Vice-President Nicolas Maduro is due to be sworn in as acting president. As such, he must call elections within 30 days.
Hugo Chavez, who led Venezuela for 14 years, died on Tuesday aged 58 after a long battle with cancer.
Mr Maduro could be seen on Friday comforting distraught mourners, who have been gathering since the early hours.
More than 30 heads of state are expected to attend the funeral including Iranian President Mahmoud Ahmadinejad, Cuban President Raul Castro and Belarusian President Alexander Lukashenko.
Mr Ahmadinejad praised Mr Chavez as a “martyr” and a “wise and revolutionary leader”.
Congressman Gregory Meeks and former Congressman William Delahunt will represent the US at the funeral of Mr Chavez, a fierce critic of Washington.
Among the regional leaders arriving on Friday was President Sebastian Pinera of Chile, who told reporters at the airport in Caracas that the thoughts of Chile were with Venezuela at a difficult time.
Mr Maduro said that Mr Chavez’s body would be embalmed “like Lenin and Mao Zedong”.
The body will be moved to the Caracas military museum where in 1992 Mr Chavez – as an army officer – was captured after leading a failed coup.
The building will be converted into a new “museum of the revolution”, Mr Maduro said.
Mr Chavez’s supporters want him eventually interred in Venezuela’s national Pantheon alongside Simon Bolivar, the 19th-Century independence leader the late president claimed as his political inspiration.
However, under Venezuela’s constitution, people may only be admitted to the Pantheon 25 years after their death.
Mr Chavez was re-elected for a fourth term as president last October after saying he had recovered from his illness.
He named Mr Maduro as his preferred successor following the recurrence of his cancer.
Reprinted from BBC