The disclosure belongs to the technical field of molecular breeding of Chinese Red Steppe cattle, and relates to a reagent, a primer, and a kit for detecting intramuscular fat content of beef cattle, and use. The disclosure provides use of a reagent for detecting a haplotype in HTR2A gene 5 in detecting intramuscular fat content of beef cattle. The use of the disclosure can provide a reference for improving meat quality of Chinese Red Steppe cattle and screening effective genetic marker genes. In addition, the disclosure provides a basis for fundamental improvement of beef quality and fat content, and production of high-grade beef. Marker 1 i3 4 500 469bp 2-1 / 2-2 2-3 2:-S Genotype CC Genotype GC Genotype CG 2-2 2-3 2-- J J Genotype GG Genotype AA Genotype GA.
