Abstract: To assess the diatom diversity of Lake Kanas, the largest freshwater lake in the Altay region, we analyzed a total of 36 diatom samples: 19 samples from the surface sediment in the lake, and 17 samples were the water of the lake, rivers and wetlands. In all, 123 taxa belonging to 46 genera were observed. Some of the 123 taxa listed are illustrated with LM and SEM photos. Among them, 13 are newly recorded species in China. They are Amphora indistincta Levkov, A. neglecta f. densestriata Foged, Asterionella edlundii Stoermer & Pappas, Discostella stelligeroides (Hustedt) Houk & Klee, Fragilaria capucina fo. sublanceolata-baikali Flower & Williams, Gomphonema makarovae Lange-Bertalot, Hippodonta geocollegarum Lange-Bertalot, Metzeltin & Witkowski, H. pseudorostrata Metzeltin Kulikovskiy & Lange-Bertalot, Nitzschia metzeltinii Lange-Bertalot, Placoneis opportuna (Hustedt) Chudaev & Gololobova, Sellaphora pseudobacillum (Grunow) Lange-Bertalot & Metzeltin, S. madida (Kociolek) Wetzel and Staurosira aff. sviridae Chudaev & Gololobova.