To investigate the role of the myomaker gene in muscle hypertrophy in Megalobrama amblycephala， the cDNA sequence was identified using RT-PCR. The developmental characteristics of muscle fibers at various stages in M. amblycephala were analyzed through paraffin sections and HE staining. Additionally， the expression patterns of the myomaker gene at different developmental stages and in different tissues of M. amblycephala were examined using real-time PCR. The results showed that the length of the myomaker gene in M. amblycephala is 4 693 bp， containing 5 exons and 4 introns. The open reading frame of myomaker is 663 bp and encodes a protein of 220 amino acids with 7 transmembrane domains. An analysis of the amino acid sequences revealed that the myomaker protein sequences were highly conserved throughout evolution， and phylogenetic tree analysis demonstrated that the myomaker of M. amblycephala clustered with that of cyprinid fish， indicating a close evolutionary relationship. The results of paraffin sections showed that the diameter of muscle fibers was significantly increased from 30 d to 60 d （P<0.05）， with the most rapid growth occurring between 40 d and 50 d. The real-time PCR results of muscle tissue at different developmental stages showed a gradual increase in expression from 15 to 30 days post hatching， peaking at 30 d （P<0.05）. Combined with morphological data， these findings suggest that the myomaker gene plays an important role in muscle fiber fusion after 30 d， thereby promoting muscle fiber hypertrophy. Furthermore， the real-time PCR results indicated that the expression level of myomaker in the muscle tissue of one-month-old M. amblycephala was significantly higher than that in other tissues （P<0.000 1）. These results demonstrate that the myomaker gene plays a significant regulatory role in the hypertrophy process of muscle fibers in M. amblycephala.