In dry and rainy seasons of 2011, an investigation was conducted on the species and density of periphytic algal communities in ten sections of Fanhe River located in northern Liaoning Province of Northeast China. A total of 47 genera, 25 families, 16 orders, 8 classes, and 6 phyla were identified, with 35 genera in dry season and 32 genera in rainy season. The periphytic algal communities in the River were mainly consisted of diatoms, followed by green algae and blue algae. The average density of the algae was 11.92×10⁵ cell·cm^-2 in dry season and 3.75×10⁵ cell·cm^-2 in rainy season. The dominant species in dry season were Synedra ulna, S. acus, Fragilaria brevistriata, F. capucina, Diatoma vulgare, Cymbella affinis, C. ventricosa, and C. cistula, and those in rainy season were Oscillatoria formosa, O. tenuis, Phormidium sp., Synedra ulna, Gomphonema acuminatum, and Cocconeis placentula. The evaluation with Shannon diversity index indicated that the water quality of the River was of slight pollution.