The invention discloses a probe, a primer and a kit for detecting seven kinds of mutations of human NRAS genes, wherein in seven groups of primers and probes from NM1 to NM7, the mutation primer in each group can be combined with a conserved sequence of the NRAS genes; the mutation ARMS primers can realize the specific binding with the corresponding mutation sequences; the mutation sequences are amplified; the detection probe can be combined with an amplification segment; the specific binding of the probe with the wild sequence corresponding to the mutation site is blocked; and the wild nonspecific amplification is inhibited. The specific mutation primer and probe blocking technology is used; the seven kinds of mutation types of the NRAS genes can be accurately detected; the built kit for a real-time fluorescent PCR (Polymerase Chain Reaction) amplification reaction system can be used for conveniently and fast detecting the mutations of the NRAS genes; the operation is simple; the result can be easily read; the sensitivity of a detection method is high; 50 copy mutations can be stably detected; the specificity is good; the 20ng wild genome DNA (Deoxyribose Nucleic Acid) does not have specific amplification; and the detection capability is as high as 1 percent.