The pearl oyster Pinctada fucata is a typical filter feeder, and is also an important marine pearl-producing oyster. In this study, the histological structure of the gill tissue in P. fucata was studied using light microscopy and electronic microscopy for the first time. The gill belongs to heterorhabdic gill type which is composed of two pieces of gill lamellas on each side of the shell cavity, i.e. inner and outer gill lamellas. The gill lamella consisted of two kinds of gill filaments-principal and normal gill filaments. The principal filaments play a supporting role in the demibranch. Nine to twelve normal gill filaments are grouped into a cluster by intrabunchial junctions between every two principal gill filaments. The normal gill filaments are linked by interfilament junctions. The epithelial cells of the interfilament junctions are a kind of flat respiratory epithelial cell, the same as that of the normal gill filaments. The existence of the interfilament junctions expands the surface area of the gill, which is helpful for exchanging air. The frontal cilia and lateral cilia on the surface of the gill filaments are responsible for carrying food particles and exchanging air. The surface cilia of normal gill filaments is a typical "9+2" microtubules structure. The results provided a background for further research on the relationship between the structure and function of gill in the pearl oyster P. fucata.