The 42-year-old faces a jail sentence of between eight and 20 years over the alleged attack.
The man, who cannot be named to protect the identity of the victim, told a court in Singapore the little girl made sexual advances on him at the time of the alleged assaults.
The court rejected his initial guilty plea as he now faces more serious charges.
He did not dispute the statement of facts presented to the court nor deny what he did.
Prosecutors said the man would commit sex acts on the child while he was in bed with her mother.
The court heard the stepdad touched the victim’s private parts only over her clothes.
It was heard his “lust for his stepdaughter grew” and his sexual assaults began to worsen.
The stepdad claimed the eight-year-old took his hands and placed them on her private parts.
Having said that, he then said he wanted to plead guilty as he felt the case had dragged on for too long and had caused him and his family undue stress.
He told the court: “Only God can help me now."
The accused could also receive at least 12 strokes of the cane.