A man allegedly murdered his wife by setting her bedroom on fire a week after she told him their marriage was over, a Sydney court has heard.

The man, who can only be referred to as AKB, is accused of murdering his wife by setting fire to their Guildford home in the early hours of October 18, 2016.

Crown prosecutor Christopher Maxwell QC told a Supreme Court jury there was evidence the couple fought during the fortnight before the fire because the woman met another man on the Viber social media messaging app.

The prosecutor said the woman had told her husband she no longer wanted to live with him and had sent him various text messages, including "I am tired of you, that is it" and "if you talk or raise your hand on me you know what I'll do, I have cut off living with you".

The court heard there will be evidence that petrol was used to start the fire.

"Very quickly it became an inferno and she was burnt to death," Mr Maxwell said.

"The accused was responsible for the fire and he intended that she die."

The prosecutor said the accused told police the fire was started by a heater and that he had tried to rescue his wife.

However, Mr Maxwell said a witness will testify that the man kept pushing his wife back into the flames and stopped her getting past the bedroom door as she tried to escape.

Mr Maxwell said there would be evidence a neighbour saw the woman at a window screaming "help me".

The court was played a triple-zero cell the woman made from the house.

In the call, the operator repeatedly asks her who she wants to be put through to and the woman can be heard screaming.

The prosecutor said the woman was 18 when they married and her husband was 35.

The trial continues before Justice David Davies.