Arthur Simpson-Kent left the UK on 19 December after the deaths of Ms Blake, 43, and their two young sons, Zachary, aged eight and Amon, aged four.
Their bodies were found buried in the garden of their family home in Erith, south London, on 5 January.
Mr Simpson-Kent is due at Westminster Magistrates' Court on Friday.
Ms Blake, who played Frankie Pierre in 56 episodes of EastEnders in 1996 and 1997, died from neck and head injuries, post-mortem tests found. She had been suffering from motor neurone disease.
Her sons also died from head and neck injuries.
Four days after their bodies were found, police officers arrested Mr Simpson-Kent on a beach in Ghana.
He was remanded in custody in Ghana on 12 January and appeared in Kaneshie Magistrates' Court in Accra.
Mr Simpson-Kent was arrested after locals recognised him from a social media photo and tipped off police.
The Met was criticised over delays in its investigation after it emerged officers spoke to Mr Simpson-Kent at the family home on 16 December.
They returned two days later to find the house empty.
But it was not until early January that the bodies of Ms Blake and her sons were found in the garden.
The Met's handling of the case is being investigated by the Independent Police Complaints Commission.
The partner of EastEnders actress Sian Blake, whose body was found in their garden, is to be flown back from Ghana to the UK later, prosecutors have said.