Xiao met the victim while they were studying English at an Auckland language school and they started seeing each other in June 2013.
By December the relationship had soured and the 20-year-old woman moved out of the flat they had shared.
Only days after she had left Xiao, he sent her messages online asking for money to pay for a large phone bill he had racked up making overseas toll calls.
When his girlfriend refused, the defendant told her that unless she gave him $1400 he would disclose something that would cause her extreme embarrassment.
Xiao also requested she cleaned the apartment as part of the arrangement.
When interviewed by police, she also told officers about the physical abuse she had suffered throughout the relationship.
The start of their courtship was punctuated by Xiao slapping and punching her in the face and the assaults escalated, court documents said.
In November, the pair argued at school about the woman allegedly looking at other men.
When they got home allegedly Xiao punched her in the stomach, held a knife to her throat then smashed her over the head with a cup.
His lawyer Michael Kan said his client was the "classic example of a Chinese only child".
"This is another sad story of a Chinese student who comes to this country... like a bird released from a cage," he said.
"A lot of his offending relates to his immaturity. He needs to learn, obviously." Mr Kan said the story had been big news in the Chinese community, with one website detailing the story getting 10,000 hits.
He argued against the offender's photo being taken because it would cause more embarrassment to the victim but Judge Ryan said Xiao should not be able to hide behind her to conceal his offending.
The judge was particularly concerned that during a pre-sentence interview Xiao had minimised the extent of his actions and blamed everyone from his girlfriend to his lawyer for his predicament.
However, probation recommended it would be unfair to jail him because of his age and the detrimental effect of mixing with hardened criminals.