The composition of phytoplankton and periphyton community in Togyo reservoir was investigated. A total of phytoplankton was composed of 150 taxa, belonging to 6 phyla, 8 classes, 15 orders, 5 suborders, 31 families, 71 genera, 106 species, 14 varieties, 1 form and 29 unidentified species. The observed number of diatoms and green algae were much higher than others. Within diatoms the pennate diatoms appeared more than centric diatoms and solitary forms or colonial forms appeared more than filamentous forms in green algae. A total of epipelic algae was composed of 125 taxa, belonging to 3 phyla, 3 classes, 6 orders, 3 suborders, 13 families, 30 genera, 87 species, 29 varieties, 2 forms and 7 unidentified species. The diatoms appeared much more than others. Among those, the pennate diatoms dominated the centric diatoms in species number observed. A total of epilithic algae was composed of 114 taxa, belonging to 4 phyla, 4 classes, 11 orders, 3 suborders, 22 families, 38 genera, 79 species, 8 varieties, 1 form and 26 unidentified species. The observed number of diatoms and green algae were much higher than others. Within diatoms the pennate diatoms dominated the centric diatoms in species number observed. The dominance of pennate diatoms of the diatom community in the epipelic algal community and the epilithic algal community could be assumed that was due to the presence of raphe structure of pennate diatoms.