Paedophile Robert Ewing, 61, was jailed for life with a minimum of 32 years for the murder of 15-year-old Paige Chivers in July, 2015.
His lawyers argued his minimum jail term was unduly severe and applied for the right to appeal on Tuesday.
But the murder had been planned and the sentence was justified, judges ruled.
Lord Justice Lloyd Jones said the trial judge was "clearly entitled" to conclude the murder was premeditated.
He noted the "extreme care" with which the killing was carried out, shown by only "three tiny bloodstains" being found at Ewing's home.
He said: "The judge was right to conclude the seriousness of the offence was particularly high."
Lord Justice Lloyd Jones said he appreciated the sentence imposed is "likely to result in Ewing spending the rest of his life in prison".
But he said reducing the sentence enough to allow any "realistic prospect" of Ewing getting out "would be wholly disproportionate to the particular seriousness of this offence".
He said: "It is simply not arguable that the sentence imposed is manifestly excessive or wrong in principle," ruled the judge, who was sitting with Mrs Justice Carr and Judge Eleri Rees.
Between 23-27 August, 2007 Ewing, who was then aged in his 50s, killed the "troubled" teenager at his flat in Blackpool.
Lord Justice Lloyd Jones told London's Appeal Court Ewing murdered Paige to "silence her" and stop her reporting the illegal sexual contact between them to police.
"Devious" Ewing knew she was an "easy target" and "how vulnerable she was and exploited it", said the judge.
A killer whose teenage victim's body has never been found is "likely" to die in jail, appeal judges have ruled.