Joe Elmore's girlfriend required reconstructive surgery after he punched her in the face during an argument at their home earlier this year, Northampton Crown Court heard.
The 28-year-old, of Dands Drive, Middleton Cheney, was sentenced to 22 months in prison after previously pleading guilty to two counts of assault, one which caused actual bodily harm.
Recorder Mark Watson said: "You abused your position of trust. You were her partner, you should have been there to care for her and protect her, not to assault her."
Severe traffic delays around Banbury due to road closure
Man jailed after leading police on a 100mph chase in Bicester
'It was simply wonderful': Swimming wish comes true for Banbury care home resident
Police want to speak to this man in connection with a handbag theft near Banbury
Driver abandons car near primary school during high speed chase in Bicester
Elmore and his partner got into an argument in the kitchen after she came home with her three and two-year-old children on April 29, the court heard.
He pushed her so she walked into the hallway. He followed her and pushed her again, so she slapped him - "not an unreasonable response," recorder Watson remarked.
"Taking place in front of your daughters, you then showed her who was boss," he said.
"You took your shirt off, wrapped it around your fist, told her you were going to punch her then did just that, punching her square in the face and breaking her nose."
Elmore's partner went to hospital for treatment but lied about what happened.
After the grabbing incident a week later, Elmore was arrested but blamed his girlfriend for everything, which recorder Watson described as a "cowardly move".
Elmore, who has a previous conviction for assault from 2016, initially denied the charges but changed his plea to guilty before an arranged trial.
As well as the jail term, he was given a restraining order so he cannot contact or see his girlfriend unless it is to meet or talk to his children.
Recorder Watson said: "Your victim was vulnerable, she had been your victim in the past.
"Her size compared to yours was slight and she was an ongoing victim of domestic violence at your hands."