A method for rapidly identifying a point mutation in porcine insulin-like-growth factor 2 intron 7 uses published primers to amplify the target DNA fragments by polymerase chain reaction. The DNA fragments are cloned and sequenced for confirmation and method validation. The key positions of the sequence are modified to generate three primers for amplifying different DNA fragments with different genotypes by PCR to avoid additional restriction enzyme digestion. A long primer is used to specifically amplify the lean muscle mass-enhancing allele, a short primer is used to specifically amplify the lean muscle mass-suppressing allele, and the third primer is shared and anneals to the complementary strand. After PCR and electrophoresis, samples with only the 92 bp band are identified as the CC genotype, samples with only the 72 bp band are identified as the GG genotype, and samples with both 92 bp and 72 bp bands are identified as heterozygotes.