The appendicular skeleton and the aculeus were examined in larvae of tawny puffer(Takifugu flavidus) from hatching through 56 days after hatching (d. a. h) by the the clearing and staining technique of cartilage and bone. According to the observation, the vertebral column started to develop from neural arches at 5 d. a. h. cartilage dyeing started at 9 d. a. h, haemal arch appeared at 13 d. a. h, bony ring appeared at 17 d. a. h, and then was ossified from front to back. The vertebral column was ossified at 29 d. a. h. In developing sequence, pectoral fin was the earliest, the anal fin followed it, and then the tail fin. The pectoral fin started to develop from the appearance of pterygiophore primordium of the pectoral fin at 2 d. a. h. The cartilaginous pterygiophore of pectoral fin formed at 28 d. a. h., and the pectoral fin was basically ossified at 42 d. a. h.. Dorsal fin and anal fin appeared in the age of 9 d. a. h, and began to ossify in the same age of 29 d.a.h. Up to 38 days of age, they were completely ossified,and branch pterygiophores appeared. The caudal fin started to develop from the appearance of pterygiophore at the end of the notochord at 11 d. a. h, and was ossified at 38 d. a. h. During this period, there are some characters followed, like pterygiophore shifted, hypural and lateral hypural developed, sickle shaped trabecular bone emerged and so on. The aculeus began to develop at 4 d. a. h with the emergence of a small amount of belly aculeus, however the scalp aculeus appeared at 16 d. a. h. All of the belly aculeus ossified almost simultaneously, but the scalp aculeus were from front to back. This study can provide the basis for the function and adaptation research, system evolution and classification of tawny puffer during its early development.