Safety monitoring on crossbeam supporting system of Three Gorges Project ship lift has been introduced in detail through the selection of monitoring objects, determination of monitoring items, arrangement of monitoring points and evaluation on monitoring results. The monitoring items include stress-strain and displacement monitoring of Bailey rack supporting system, deformation monitoring of tower column, verticality and displacement monitoring of bent. By comparing the monitoring results with the data acquired from prototype load tests, it shows that the crossbeam supporting system is very safe and reliable during the construction progress. At the same time, all the monitoring indexes can meet the design requirements. Meanwhile, the safety monitoring plan and technology system can provide a reference for the safety monitoring of other similar projects.