The man convicted of killing Wellington woman Mei Fan is appealing both his conviction and sentence.

Michael Preston was last year sentenced to life in prison with a minimum non-parole period of nineteen years for his estranged wife's murder.

He stabbed  Fan thirty-eight times before her body was found in a pool of blood at her Miramar home in November 2013.

Preston's lawyer Steve Gill told the Court of Appeal this morning that the case was circumstantial and there was no smoking gun.