A young woman's ex-partner allegedly tried to force her to commit suicide while holding her captive in her North Perth unit for two nights this week.

Western Suburbs Det-Sgt Jason Blaine said it would be alleged that the man forced his way into the woman's unit on Tuesday and during a terrifying two days, made her take tablets and told her he wanted them to die together.

"She spat them out when he was not looking," Det-Sgt Blaine told thewest.com.au.

The man also allegedly tied some kind of tie around her neck at one stage and held onto it so she could not leave.

The pair had been together for two years before breaking up in February.

The woman was allowed to go to work on Thursday after convincing the man they were back in a relationship, Det-Sgt Blaine alleged.

A 25-year-old Ballajura man has been charged with aggravated burglary, depravation of liberty and threats to kill.

He is expected to appear in Perth Magistrate's Court today.

PERTH GABRIELLE KNOWLES