The rally is being held on October 18, the day Bilawal's mother and slain Prime Minister Benazir Bhutto returned to Pakistan after eight years in exile in 2007 and was attacked in twin blasts at Shahrah-i-Faisal.
Militant groups had attacked Benazir's rally, killing about 140 people and injuring over 400 others.
Political analysts say that Bilawal has made a calculated decision to hold the rally on October 18 to launch his political career in a big way and present himself as the true successor to the Bhutto's political dynasty.
The PPP, which is the ruling party in the southern Sindh province, is optimistic about a massive turnout for the rally which will be held at the Bagh-e-Jinnah, a public park adjacent to Muhammad Ali Jinnah's mausoleum.
Also Read
Seating arrangements have been made for about 150,000 people.
"It is a huge occasion for the party as this will be Bilawal's first public rally in Karachi and also the first big rally by the PPP in the city after a long time," Sindh information minister Sharjeel Memon said.
The rally is also seen as significant as for years now the Muttahida Qaumi Movement (MQM) which represents the Urdu speaking population has held massive rallies that other parties have not been able to match in numbers.
Last month, Imran Khan and his Pakistan Tehreek-e-Insaaf party also held a rally at the same venue, Bagh-e-Jinnah, that attracted a very big crowd.
Bilawal and the PPP have promised a historic turnout on Saturday.
"There should be around 3000 policemen and paramilitary rangers as part of the security plan for the rally," a government official said.
Bilawal, who has already launched his political career on social websites, visited the rally site today with other party leaders to review the arrangements.