A Perth man who bashed his 64-year-old father, leaving him with life-threatening injuries, has been jailed for three years and four months.

The father was repeatedly punched and kicked after he tried to intervene in an argument the 36-year-old offender was having with his mother at their home in March last year.

The District Court of WA heard on Wednesday the father was grabbed around the neck, dragged to the ground and punched up to 20 times during the first of three assaults.

He had seizures in the ambulance on the way to hospital, where he was found to have suffered bleeding in and around the brain.

He was placed in an induced coma and spent five days in the intensive care unit.