Seasonal variations of the optical parameters and physicochemical properties of lake water at 15 sampling sites were investigated, from July 2009 to June 2010, to provide the basic lake optical properties data for submerged aquatic vegetations restoration of a shallow lake-Lake Gehu. The annual variation of the attenuation coefficient of photosynthetically active radiation (K_d) was 1.32-17.42 m^-1. The minimum and maximum values of K_d were observed in autumn (1.32-3.70 m^-1) and summer (3.68-17.42 m^-1), with a medium value of 2.35 m^-1 and 6.23 m^-1, respectively. The average euphotic zone depth in spring, fall and winter can satisfy the demand of submerged aquatic vegetation. However, the average euphotic zone depth was only 0.84 m in summer, which was less than the average water depth(1.20 m) of Lake Gehu and implied that the photosynthetically active radiation was one of the inhibiting factors to restore the submerged aquatic vegetations in summer. The K_d and secchi disk depth (SD) in fall and winter had the relationship of K_d=2.089 + 0.705/SD. Chlorophyll-a and suspended solid were the factors influencing the K_d value in Lake Gehu.