An estranged husband who stabbed his wife 12 times in the back and slashed both of her cheeks with a kitchen knife to deliberately maim her has had his prison term increased.

Prosecutors appealed against the sentence handed to Alen Naumoski for the brutal 2011 assault on his wife Biljana, who almost died in her own home from blood loss and a ruptured spleen after being repeatedly stabbed.

The court heard Naumoski laid in wait for his wife to return home before launching the attack, which was intended to "deliberately maim his beautiful wife so as to render her no longer beautiful".

Following the attack, Ms Naumoski lost the use of one hand, and the use of her thumb on the other hand, is unable to work or drive, and lived with depression, fear and feelings of self-loathing.

Naumoski was originally jailed for five years - with eligibility for parole after three - after a charge of attempted murder was downgraded to grievous bodily harm with intent, which he admitted.

But after Ms Naumoski vented her anger, and prosecutors appealed, WA's Court of Appeal agreed the sentence was 'manifestly inadequate' and increased it to seven years in prison.

Justice Carmel McLure said Naumoski's assault was among the worst of its type ever seen in the state.

"The premeditated confrontation, the ferocious and sustained attack, the nature and extent of the intentionally inflicted harm and its tragic effect on the life of the victim justify that assessment," Justice McLure wrote.

"What significantly aggravates the offending is that not only did the respondent intend to do the victim grievous bodily harm, he also intentionally disfigured the victim's face and other parts of her body."

Naumoski will now be eligible for parole in September 2016.