A man accused of throwing his fiancee off a high-rise balcony will stand trial for her murder.

Simon Gittany, 39, has pleaded not guilty to murdering Lisa Harnum by pushing her off the balcony of their apartment in Sydney's CBD on July 30, 2011.

Magistrate Clare Farnan ruled in Downing Centre Local Court on Friday that there there was enough evidence to commit Gittany to stand trial over her death.

Ms Farnan accepted that the prosecution case relied heavily on the account of a witness crossing Hyde Park who saw an object he believed at the time was a duffel bag being dropped from the balcony.

It was only when he got closer that the witness realised the object was a person.

Ms Farnan said that if a jury accepted the key witness's evidence it could be crucial in convicting Gittany of murder.

She said the prosecution case relied to a "very large degree" on his evidence.

"A properly instructed jury could accept that he saw an unloading motion of an object," she said.

The magistrate said CCTV evidence from inside the apartment building showing Gittany dragging Harnum back inside their unit, and accounts from neighbours who heard screams also contributed to her decision.

She said some evidence pointed to Gittany's innocence, including the fact he had told police about the existence of CCTV footage.

Gittany, who appeared in court wearing a dark suit and with many supporters, maintained his plea of not guilty and reserved his defence.

He will be formally arraigned in the NSW Supreme Court on February 1.