The invention discloses an FDFT1 (farnesyl-diphosphate farnesyltransferase 1) gene key loci affecting Chinese simmental cattle fat deposition, and relates to a detection method for single-nucleotide polymorphism of Chinese simmental cattle fat deposition trait related FDFT1 gene. The method takes Chinese simmental cattle genomic DNA or a DNA sequence containing the Chinese simmental cattle FDFT1 gene as the template, and utilizes the PCR primer pair P1 and P2 to amplify a Chinese simmental cattle FDFT1 gene functional region fragment, and by means of sequencing screening, restriction endonuclease Hae-III and Hpa-II enzyme digestion, and electrophoretic analysis, the 130th SNP1 (T greater than C) of a 4th intron in the Chinese simmental cattle FDFT1 gene and the 500th SNP2 (C greater than T) of a 8th exon can be determined. In the screening obtained SNPs, the T allele and TT genotype of the SNP1 locus and the C allele and CC genotype of the SNP 2 locus can serve as the effective molecular genetic markers for significantly improving Chinese simmental cattle fat deposition and inter-muscular fatty acid traits so as to be used for beef cattle meat quality trait early marker assisted selection of molecular breeding.