The construction monitoring method of cast-in-situ cantilever rigid frame bridge is introduced,which includes structure analysis,data collection in field,parameter identification,model modifying and construction instruction. By data cellection in field,model modifying,command-giving,the designing status of the bridge is guaranteed. Taking the Dapo Guijiang bridge of Majiang-Wuzhou Expressway Project for example,it is introduced the monitoring method. The measured data show that excellent effect has been got by the monitoring method.