Analysts say the reforms are meant to address longstanding public grievances in the North African nation, and possibly to prepare for a smooth transition amid concerns over the health of 78-year-old leader Abdelaziz Bouteflika.
The president and his inner circle have held a firm grip on power since 1999 and, as the end of his rule appears to close in, there are fears of instability in the mainly Muslim country of 40 million, a key energy producer.
Dominated by Bouteflika supporters, Algeria's lower and upper houses are expected to adopt the reforms on Sunday.
An opening ceremony for the special session was held on Wednesday and the full package is to be presented by Prime Minister Abdelmalek Sellal on Thursday.
Parliamentary group leaders will be able to make speeches on the constitutional reforms but there will be no open debate. The package must be voted on in full, not amendment-by-amendment.
The main political reforms will see the reintroduction of two-term limits on the presidency -- lifted in 2008 to allow Bouteflika to run for a third time -- and a provision requiring the president to nominate a prime minister from the largest party in parliament.
An independent electoral commission will also be established, the roles of women and youth will be recognised, and freedoms of assembly and the press explicitly guaranteed.
The Amazigh language spoken by the indigenous Berber population will also be recognised as official, alongside Arabic.
The reforms "strengthen freedoms and enshrine the separation of powers and the principles and values of the Algerian people", Ahmed Ouyahia, Bouteflika's chief of staff, said last week.
Critics disagree, saying the reforms are little more than a show and will do little to reduce the influence of the powerful elite, including Bouteflika's National Liberation Front (FLN) party and army generals, who dominate the country.
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"This constitutional reform project does not have the concerns of Algeria at its heart but only the current political regime which it is designed to protect," said Ali Benflis, a former prime minister who ran against Bouteflika in 2004 and 2014.
The Front of Socialist Forces (FFS) opposition party, whose 30 lawmakers have said they will boycott the vote on the reforms, said the project was "nothing more than the continuation of the tradition of constitutional violence against the Algerian people".
John Entelis, an Algeria expert at Fordham University in the United States, said the reform package was clearly designed to address public concerns.
"Each of these newly inscribed constitutional rights is directed at assuaging the discontent so evident among Berbers, women, youth, civil society activists and political opponents," he wrote last month in The Washington Post.
"Yet given the way this document has been conceived, communicated and constructed, almost all of the discontented groups remain unconvinced that the rhetoric of the state... will in fact be translated into political action."
Bouteflika has rarely appeared in public since suffering a stroke in 2013 and there has been widespread speculation of a behind-the-scenes power struggle over his succession.
The president and his supporters have moved in recent months to take control of the shadowy security services, dissolving the powerful Department of Intelligence and Security (DRS) and jailing or sidelining top officials.
Unlike many countries in the region, including its neighbours Libya and Tunisia, Algeria has been relatively stable since the 2011 Arab Spring.
But it is facing a range of challenges, including regular jihadist attacks, sporadic outbreaks of violence between Berbers and Arabs, and a precipitous drop in state revenues as oil prices have plummeted.
The reforms will also see dual nationals banned from holding high public office, a move that has angered many among the hundreds of thousands of Algerians who also have citizenship in France, the former colonial power.