Abstract: The ground penetrating radar(GPR) is applied in French Fives Cail Babcock(FCB) shield machine with a diameter of 6.34 meters for frontal detection.Based on the mechanical modification of cutter disc,the real-time images of frontal geological information can be transferred to the control room at the end of the shield machine through cable and wireless transmission.The analysis system for frontal detection is established using the databases of geological types,obstacles and radar images.The detection of the geological situations in front of the excavation surface through the analysis of current radar images provides the basis for the accuracy and safety of shield machine construction.The theoretical analysis and experiments indicate that the real-time geological detection based on this frontal detection system is feasible,and is of creativity and practical engineering value.