In the observation of diatom samples from Dianshan Lake, Shanghai, China, two species are new records of China. They are Cyclotella costei Druart & Straub and Sellaphora pseudoventralis (Hustedt) Chudaev & Gololobova. For the two newly reported species, morphological characters, habitat and distribution were described in detail. It enriched the biodiversity of diatoms in China.