Three polymorphisms were identified in the sixth intron of the CAST gene by PCR-RFLP using enzymes Msp I, Hinf I and Rsa I in 45 Jinpi F2 pigs. However, only three genotypes AACCEE, BBDDFF, and ABCDEF were detected in those pigs and the genotype frequencies were 0.1778, 0.2222 and 0.6000, respectively. Longissimus dorsi muscles were moved for paraffin serial sections and stained with hematoxylin-eosin or myosin heavy chain (MHC) by immunohistochemistry respectively. Fiber cross-sectional area, fiber density, fiber diameter, the rate of MHC type I fiber and the carcass characteristics were recorded. Correlation analysis showed that the skeletal muscle fiber area and the eye muscle area of the BBDDFF individual were significantly higher than those of the ABCDEF individual (P < 0.05).