A man accused of abusing and murdering his girlfriend's seven-year-old son and blaming the death on an accidental fall from a pogo stick, will face trial in October.

The 31-year-old man, who cannot be named for legal reasons, is charged with more than 20 offences including murder, common assault, inciting an act of indecency, and assault occasioning actual bodily harm.

He appeared in the NSW Supreme Court on Wednesday, via audio-visual link from jail, to hear that he would face an eight-week trial from October 6.

The boy's mother on Tuesday pleaded guilty to the boy's manslaughter.

An autopsy found the boy had a "plethora of injuries" including a fractured skull, fractured ribs and bruising consistent with repeated physical abuse.

Police said the mother failed to seek medical help after the boy was seriously injured, despite him being unresponsive and failing to improve over several hours.

The woman will face a sentencing hearing on May 8, the same day the man is due to be arraigned in the Supreme Court.