A kind of modularized and air adjustable constructed submerged plant bed (CSPB) was used to restore the eutrophic water. This CSPB helps hydrophytes to grow up under poor conditions, like frequently changed water depth, blurred water transparency, algae bloom and duckweed rampant in summer, which are not suitable for growing water plants naturally. The experiments in Waihuan River of Tianjin show that total phosphor (TP) reduces 30%-40% in growing season and 7%-20% in winter when the detention time is 5.48 days. The variation between the concentration of TP and the detention time follows the first-order kinetic equation, the correlation coefficients (R2) is above 0.9. The attenuation coefficients k of the kinetic equation changes with the water temperature. When the water temperature is quite low or quite high, the value of k is not significantly changed with the temperature of water. While when the temperature is in a moderate range, an increase of water temperature leads to a rapid increase of k value.