The event in the capital will mark the end of a 110km march from Brighton by human rights campaigner Peter Tatchell.
He will stage a mock citizen's arrest of a man wearing a Mugabe mask after he unsuccessfully attempted to arrest the president in 1999 and 2001.
Up to 30 exiled Zimbabweans and victims of torture will attend the vigil, which will start with a prayer.
Sally Mutseyami, one of the organisers from the Restoration of Human Rights in Zimbabwe group, told Premier: "This time has come for us, we need prayer, we need God to guide is, we need all Christians everywhere to pray for us and also prayer for human rights campaigners who get arrested every time they speak up."
A protest movement called This Flag has been gathering momentum in Zimbabwe with regular protests. Police have been using rubber bullets and batons to break up the demonstrations. Hundreds of people have been injured.
Mutseyami added: "It's only us Zimbabweans who can bring the change that we need in Zimbabwean and it takes us back to when Moses was in Egypt - the Israelites had to stand together around one idea to free themselves because the time had come."
She said many Christians had been imprisoned "just for wanting to stand for what is right".
"Let us pray against those dark forces that continue to hold us in bondage and liberate Zimbabwe," she added.
Embattled President Robert Mugabe has accused the West of organising protests against him "like in the Arab countries".
Earlier this month Premier reported how the Archbishop of York Dr John Sentamu said the country has "become rubble" during Mugabe's leadership.
The Archbishop said: "Step down while there is time, and allow someone else to take over Zimbabwe and rule it, so they'll be no violent coup which again will drive people more and more into poverty.
"Please just step away for the sake of Zimbabwe."
Listen to Premier's Antony Bushfield speak to Sally Mutseyami:
