Abstract: The BL4 beam of Geheyan ship lift is an important structure connected between the upper head and the middle aqueduct of the second vertical ship lift. In order to decrease the tensile stresses , prestressed anchors were installed on the BL4 beam. Some strain sheets were installed on the surface of concrete to monitor the distribution of stress during installing prestressed anchors. The monitoring result indicated that the compressive stress increased with increase of prestress of anchors, the maximum value was up to -5.54 MPa, and there was no tensile stress . So the effect of prestressed anchor is very good.