Abstract: The imaging of pipes in a water-filled tank is investigated using aground penetrating radar(GPR)with an antenna of 1.6 GHz center frequency.The radar profiles of metal and polyvinylchloride(PVC)pipes in different conditions such as depths,diameters,dielectric losses are achieved.A numerical simulation program of two-dimension finite difference time domain which can model a pipe of thin wall is built to compare with experiments.The results of numerical simulations are in good agreement with experiments.This paper discusses the differences and similarities of actual detect and simulated radar profile in an interpreted point of view.A series of hyperbola caused by the multiple reflections of electromagnetic wave between object to be detected and surface is analyzed.Slight differences between results of simulation and actual detect with relative high-loss dielectric are also investigated.