A recursive back projection(BP) imaging algorithm is presented.Real time imaging is an intense demand but a challenging task in impulse surface penetrating radar(ImpSPR)’s application.Based on 'delay-sum’ operation in time domain

BP imaging algorithm can precisely focus scattering intensity and obtain high quality subsurface profile.But its heavy computation load restricts its application in ImpSPR's real time processing.After analyzing BP imaging procedure

a recursive model of this imaging algorithm is established and recursive BP imaging algorithm is educed subsequently.The computation complexity of both original BP imaging algorithm and recursive BP imaging algorithm are analyzed.Through processing experimental data obtained by a ImpSPR system-RadarEye

the recursive BP imaging algorithm validate its capability at the aspect of ImpSPR's real time processing.