Lord Edward Somerset, 55, admitted four counts of assault occasioning actual bodily harm against his wife, Lady Caroline Somerset, between 1990 and 2012.
The attacks - in which Lady Caroline suffered bruising, scratching, hair pulling and a fractured finger - took place on the sprawling Badminton Estate in Gloucester, where the couple lived.
Bristol Crown Court heard Somerset became enraged and assaulted his wife when she confronted him about his addiction to drink and drugs including heroin and cocaine. In 2011, Lady Caroline received an "incredibly hard" kick to her foot after challenging her husband when he moved his new girlfriend into their home while they were married.
She required hospital treatment last year from two attacks after arguing with her husband after he took crack cocaine in front of their youngest daughter.
Judge Mark Horton said the attacks left Lady Caroline in "emotional turmoil".
He also imposed a restraining order to protect Lady Caroline, who is in Australia, from her estranged husband.
Divorce proceedings between the couple are set to be finalised soon.