Pistorius's lawyers had applied for leave to appeal to the Constitutional Court, the highest court in South Africa, arguing that the Supreme Court of Appeal (SCA) had wrongly upgraded his conviction to murder.
But the National Prosecuting Authority (NPA), which opposed the application, said the appeal bid had failed.
"The court dismissed the application for leave to appeal because there are no prospects of success," NPA spokesman Luvuyo Mfaku told AFP.
The former Paralympic champion, 29, will attend a sentencing hearing in Pretoria on April 18.
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The minimum 15-year jail term for murder may be reduced due to time he has already spent in prison.
The double-amputee killed Reeva Steenkamp, a model and law graduate, on Valentine's Day three years ago, saying he mistook her for an intruder when he shot four times through the door of his bedroom toilet.
He was released from jail in October to live under house arrest at his uncle's property in Pretoria after serving one year of his five-year prison sentence for culpable homicide -- the equivalent of manslaughter.
They found him guilty of murder, overruling the culpable homicide conviction.
Legal papers filed at the Constitutional Court by Pistorius's lawyers contended that the SCA had "acted unlawfully and unconstitutionally".
They also accused the SCA of making "errors of law" over the principle of "dolus eventualis" -- awareness of the likely outcome of an action -- which has been at the crux of the long-running case.
But most experts had dismissed his chances of success in the Constitutional Court.
"The trial court now will take into account his personal circumstances and decide on a suitable sentence.