A morphology study is carried out on three freshwater species of Gyrosigma (Gyrosigma obtusatum, G. kuetzingii and G. sciotoense) using light and scanning electric microscopy to demonstrate their fine structural characters, and the regions of their geographical distribution in China are also summarized. The results show that: (1) all three species belong to the section Strigiles and all present two types of valve outline in valve view: Sshaped and reverse Sshaped (Sshaped); (2) G. obtusatum has weakly sigmoid valve outline, Tshaped external proximal raphe fissures, straight internal proximal raphe ending, and elliptic central area; G. kuetzingii bears distinctly sigmoid valve outline, external proximal raphe fissures which slightly deflect towards different sides, straight internal proximal raphe ending, and elliptic central area; and G. sciotoense possesses also weakly sigmoid valve outline, strongly hooked external proximal raphe fissures, Tshaped internal proximal raphe fissures, and oblique central area; (3) G. obtusatum is found in Guangdong, Guangxi, Hunan, Sichuan and Yunnan; G. kuetzingii is found in both Xinjiang and Hunan; and G. sciotoense is only discovered in Wuling Mountains, and this is its first report from the freshwater in China.