The State of the Nation address is an annual mix of political pageantry and policy announcements, but the flagship event was postponed last week as Zuma battled to stay in office.
He was forced to resign on Wednesday after the ruling African National Congress (ANC) party turned against him, and pro-business reformist Ramaphosa was sworn in as president on Thursday.
The fight against corruption, allegations of which dogged Zuma and badly dented investor confidence, are expected to feature prominently in the speech, due to be delivered to parliament in Cape Town at 1700 GMT.
He vowed to use his address "to outline some of the steps we are going to be taking" against graft.
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Arriving at parliament on Friday, Ramaphosa told journalists he was "a little bit excited, expectant, a little apprehensive" ahead of the speech, but said he was looking forward to the evening.
After multiple corruption scandals, economic slowdown and falling popularity among voters, the ANC had threatened to oust Zuma via a no-confidence vote in parliament.
Zuma reluctantly resigned, saying he had received "very unfair" treatment from the ANC.
"Ramaphosa will probably remove many Zuma allies in a cabinet shuffle, but only after the budget speech on 21 February," predicted Eurasia Group analyst Darias Jonker.
"(He) will also go after high-level corruption, particularly the Gupta family and their associates, which include members of the Zuma family.
"This campaign will greatly contribute towards restoring investor confidence."
The Guptas are a migrant Indian business family who formed allegedly improper ties to Zuma. They are accused of receiving hugely favourable government deals and even influencing cabinet appointments.
The COSATU trade union federation, an ANC ally, called on Ramaphosa to slim the executive and crack down on government excess.