An ultra-wide band through-wall point target positioning imaging method which is based on the back projection algorithm relates to a radar arrangement method and a positioning and imaging technology of positioning and imaging under a limited distance. The invention has the purpose of avoiding the occurrence of the pseudo image phenomenon. Signals output by an ultra wide band signal source are output into two passages of signals c1<*> , c2<*> after passing through a power divider; the c1<*> passes through a selection controller, an amplifier and a first emitting radar and then outputs pulse signals d1; echoed signals h1 which are generated by the d1 pass through a first receiving radar and a first amplifier with low noise-signal ratio and then signals e1,1 are obtained; the h1 passes through a second receiving radar and a second amplifier with low noise-signal ratio and then signals e1,2 are obtained; the c2<*> is respectively correlated with the e1,1 and the e1,2 and then a propagation time series a1,1 and a propagation time series a 1,2 are obtained; a point target location series Target1 is obtained through the point target positioning processing of the a1,1 and the a1,2; the steps from one to seven are repeated to obtain a point target location series Target 2 after a first emitting radar Tx1 is replaced by a second emitting radar Tx2; the intersection of the Target1 and the Target2 is taken as the actual point target location series to send into an image generator to complete the point target positioning imaging.