The amount of photosynthetically active radiation (PAR) in the water column is of fundamental importance in determining the growth of aquatic plant and aquatic primary production. Light attenuation in aquatic ecosystems has important ecological implication and water quality applications. In the present study, the light attenuation through the water column in the Shihmen Reservoir, Taiwan was measured. A light attenuation coefficient (Ke) can be derived from the PAR measurements at each stations. The linear regression analysis reveals that Secchi disk depth is a sample alternative measure of light transmitability and provides a reasonable estimate of the light attenuation coefficient in the Shihmen Reservoir. We conducted multiple-regression analysis for the Ke, chlorophyll a, and total suspended solids (TSS). Because the concentration of chlorophyll a is roughly <5 μg/L in the Shihmen Reservoir, the chlorophyll contribution to the attenuation coefficient will be <0.1 m-1, which is negligible. Ke correlated with TSS concentration yields a good correlation, indicating the TSS should be a good water quality variable for predicting water column light attenuation coefficient in the Shihmen Reservoir.