Abstract: 【Objective】Explored the detailed characteristics of Hippocampus trimaculatus skeletons, provided technical support for the type identification of H. trimaculatus, and accumulated data for the basic biology of H. trimaculatus.【Method】On the basis of the transparent skeleton dyeing method, a special staining method for H. trimaculatus was improved to describe its skeleton characteristics, and the skeleton characteristics of H. trimaculatus were described in detail.【Result】Compared with the traditional transparent skeleton staining method, at decolorization and transparency procedures, the improved transparent skeleton staining method effectively removed the tissue residue with the addition of a small amount of H₂O₂, and a small amount of 2% KOH to make the tissue more transparent, and the placement of H. trimaculatus skeleton samples upright in the bottling step. The number of dorsal fins in H. trimaculatus was 19-21, and the number of pectoral fins was 18-19. The head of H. trimaculatus had its unique structure:many salient apines, the jaw skeleton formed a tubular structure, and there was no gill hole at the trailing edge of the gill cover. The opening of the gill hole was directly above the head of the gill. H. trimaculatus was covered by a ring of diamond-shaped skeletons from head to tail body surface to provide protection and support for it. There were 12 bone rings in the chest and abdomen. Except for the 11th and 12th section, each ring of the thorax and abdomen is composed of 7 irregular diamond-shaped skeletons. There was a unique sliding structure inside and between the skeleton rings, which provided a three-dimensional space for movement and feeding. Each ring of the tail skeleton was composed of 4 diamond-shaped skeletons. There were 40-41 bone rings in the tail, each ring is composed of 4 diamond-shaped skeletons, and the skeleton pieces shrink toward the tail gradually form a square skeleton ring and there was a sliding structure between the skeleton rings to provide activity space for the climbing action.【Conclusion】The improved transparent skeleton staining method is more suitable for H. trimaculatus skeleton dyeing, with convenient operation and high quality of skeleton specimens. H. trimaculatus has a unique head skeleton structure and feeding mode. The whole body below the head is surrounded by the skeleton, and the exoskeleton is mainly composed of rhomboid skeleton. However, the number of rhomboid skeletons constitute different rings in different parts;there is a sliding structure inside and between the bone ring to provide stereoscopic space for the movement and feeding of H. trimaculatus, so the nutrition status of H. trimaculatus and the gonadal development of the female H. trimaculatus can be determined through the chest and abdominal expansion circumference.