The invention belongs to the technical field of molecular markers, particularly relates to a molecular marker related to pig muscle fiber area and intramuscular fat content, a detection method and application of the molecular marker, and aims to obtain a molecular marker related to pig muscle fiber area and intramuscular fat content, and establish a method for determining the pig muscle fiber areaand intramuscular fat content within a short time, thereby determining meat tenderness, and assisting in breeding. The technical scheme is as follows: a specific primer is designed according to the INDEL mutation site of the TNNC2 gene on the first exon, amplification is carried out, and the polymorphism detection is carried out on the site by using restriction endonuclease BsmAI, thus the size of the muscle fiber area and the intramuscular fat content between the pig individuals are distinguished according to the polymorphism detection results.