We designed a new device which can be used to measure the absorption coefficient of pure water directly.First

we measured the irradiance of direct light penetrating through different thicknesses of water layers.Then we used the ratio method to eliminate the impact of measuring instruments on experimental results.Finally

we acquired the extinction coefficient.The extinction coefficient experiment proved that extinction coefficient of suspended substance in water can be calculated by formula of ?ngstrom.We therefore put forward a method on how to eliminate the impact of suspended substance in pure waters.Eventually

we determined the absorption coefficient of pure water from 400 nm to 900 nm.Comparing with previous studies

overall results are consistent

but with better precision in the long wave length.The absorption coefficient of pure water can be used as the normal data for water quality remote sensing.