Abstract: The aim of this study was to explore the polymorphism of CAST gene and its effects on meat quality traits in hybrid offspring of northeast fine-wool sheep and German mutton sheep. Blood samples of 93 healthy crossbred sheep were collected for DNA extractin, PCR amplification and PCR-SSCP analysis. The biceps femoris, triceps brachii and Longissimus dorsi muscles of 10 German mutton crossbred sheep were collected for determination of meat color, pH value, shear strength and cooking loss rate. The results showed that only mutation site（G332A） in exon 7 of CAST gene were found in exon 6-8 of CAST gene in crossbred sheep. There were three genotypes in exon 7 of CAST gene, namely AA, AB and BB genotypes. There was no significant difference in meat color and pH value of biceps femoris, triceps brachii and longissimus dorsi of German mutton sheep among the three genotypes. There was no significant difference in shear force between AA genotype and AB genotype, but had significant difference in BB genotype（P＜0.05）, the cooking loss rate of biceps femoris, triceps brachii and longissimus dorsi had no significant difference in AA and AB genotypes, but there was significant difference between BB genotype and AA and AB genotypes（P＜0.05）. There was no significant difference in cooking loss rate between AA genotype and AB genotype（P＞0.05）, but there was significant difference between BB genotype and AA genotype（P＜0.05）. The results indicated that the polymorphism of CAST gene was significantly correlated with the shear stress and cooking loss rate of German-finer cross sheep, and the BB genotype individuals could be selected to improve their muscle tenderness during the breeding process.