Jamal Mokohore Watana hit his ex-partner to the ground during an argument, then spat on her.
Watana had been separated from the victim for 18 months, and they have two children together, the Whanganui District Court heard on Tuesday.
An argument started between the two and escalated to Watana punching the victim in the face, then backhanding her, causing her to fall to the ground.
After spitting on her, Watana took the victim's phone and threw it at the wall, breaking it, police prosecutor Sergeant Stephen Butler said.
Watana then took one of the children and left the house.
When he was spoken to by police he admitted the assault, and said it was due to something the victim had said.
Watana pleaded guilty to male assaults female and wilful damage. Defence lawyer Roger Crowley noted none of his client's previous criminal offending related to domestic violence.
Judge David Cameron sentenced Watana to 100 hours of community work and made a protection order in favour of the victim and the children.