Derek Barrett has been sentenced to a maximum of 46 years behind bars for the "sadistic" stabbing murder of his niece in April 2016.

University student Mengmei Leng - also known as Michelle - was tied up and killed by Barrett, her aunt's husband, at the home they all shared at Campsie in Sydney's west.

Two days later, her naked body was driven more than 100 kilometres away and thrown off a cliff into a blowhole at Snapper Point on the Central Coast. It was spotted by tourists hours later.

On Friday, Justice Helen Wilson sentenced Barrett, 29, to at least 34 years and six months in prison for his crime, with a maximum of 46 years. He will be eligible for parole in 2050.