In most fish, slow and fast muscle fibers occupy distinct regions in the axial muscle and display different growing characteristics. To fully understand the postembryonic development feature of slow muscle fibers of Mandarin Fish (Siniperca chuatsi), we made paraffin section at the base point of the dorsal fin on individuals at age 1 to 33 days and dyed paraffin section by immunohistochemistry method. We also identified the number of slow muscle fibers and measured their area by using image analysis software. The results showed that slow muscle fibers located near the horizontal septum after hatching with a wedge shape, later they extended to the dorsal and ventral. At age 1 to 9 days, the slow muscle fibers were monolayer, then they became multilayers at age 11 days. Slow muscle fibers covered across the lateral line at age 19 days, then extended to the second dorsal myotome and down to 2/3 of ventral myotome and became into two muscle fiber sections at 33 days, which were located at the horizontal septum and lateral line, respectively. The superficial, spindle cells of skeletal muscle may were the main source of slow muscle fibres hyperplasia growth. The total numbers of slow muscle fibers increased from 6 to 315 after hatching, and the total fiber area increased from 13.18 μm² to 7 839.58 μm². Hyperplasia growth of muscle fiber was dominant at age of 13 days, where as hypertrophic growth was dominant at the other ages.