Nutrient limitation and light limitation was examined for the Youngsan Lake by collecting chlorophyll $alpha$ and other properties including light intensity, nutrient concentrations, pheopigment ratio monthly from March, 2003 to April, 2004 (except for November-January). Chlorophyll $alpha$ was fractionated into net-(>$20;{mu}m$) and nano-size(<$20;{mu}$). Light and nutrient limitation index was calculated based on the equations incorporating the mechanisms of limitation of light and nutrients from the literature. Phytoplankton population (chlorophyll $alpha$) was low during the wet season especially in August and increased in short-period during other seasons. Photoperiod was short during the wet season but long during the dry season. Nutrients such as phosphate and ammonium were rapidly increased in spring, 2004. Light limitation index was minimum (0.01) in August during the wet season and nutrient limitation index was relatively high (>0.4) except for May and September. Light limitation may affect phytoplankton growth rather than nutrient limitation considering that nutrient levels are high in the Youngsan Lake. Results of correlation analyses showed a negative correlation between light and nutrient limitation indices and net-pheopigment index, and a positive correlation between the indices and nano-pheopigment index. These results suggest that phytoplankton response to change of light and nutrient may be size-dependant.