Dennis John Larsen pleaded guilty to one charge of male assaults female in Masterton District Court this week.
Larsen, 18, appeared in court on Thursday represented by lawyer Ian Hard.
Police prosecutor Sergeant Garry Wilson said Larsen pushed his partner to the ground after an argument on February 27.
The woman hit her head on a stereo system, and Larsen then punched her thigh three times. He then threw her on the bed and used his right hand to strangle the woman until she couldn't breathe. He released her and she managed to call police.
Larsen told the court he went into a rage and was unsure what had happened. He admitted he had problems with anger.