Thousands of angry protesters demanding her removal are outside the National Assembly's main gate.
Ms Park is embroiled in a political scandal that has sparked many protests.
At the heart of this scandal is the relationship between Ms Park and a confidante, Choi Soon-sil, accused of using connections to gain influence.
Prosecutors say Ms Park had a "considerable" role in the alleged corruption, which she has denied.
She has also resisted calls to step down, insisting that she would leave the decision up to parliament.
South Korea's parliament introduced the impeachment motion on Thursday, which will go through if at least two thirds of the assembly vote in favour of it - something which observers say is likely.
The assembly is dominated by opposition parties and independents who want her dismissed - but they need at least 28 more votes from Ms Park's Saenuri party for the impeachment.
Reports say there may be enough Saenuri dissenters who would vote for it. Ms Park said this week that she would accept the vote's outcome.
If parliament votes for impeachment, Ms Park would not be immediately removed. She would only be suspended from office, with the prime minister taking over her duties.
The decision would still need final approval from the nine-judge constitutional court, which would have six months to deliberate.
If it upheld the decision, only then would Ms Park be dismissed. She would become the first sitting South Korean president to be deposed in the country's democratic era.
At the heart of the scandal is Ms Park's links to Ms Choi, who has already been charged with coercion and abuse of power.
Ms Choi is accused of using her links with Ms Park to pressure some of the country's biggest corporations into donating to two foundations controlled by Ms Choi, who allegedly siphoned off funds for her personal use.
On Tuesday the corporations' leaders were grilled by MPs in a rare parliamentary enquiry on whether they made the donations in exchange for political favours.
Ms Park has also come under fire for allowing Ms Choi inappropriate access to government decisions, something which she has repeatedly apologised for.
The scandal has ignited public fury in South Korea, where tens of thousands of people have staged demonstrations in Seoul in recent weeks calling for Ms Park to step down.