Five scaled model tests of reinforced foundation with different reinforcement length and depth(layer numbers)as well as one contrast test of unreinforced foundation were carried out using transparent technique.The evolution of displacement field in the reinforced foundation and procedure of slide failure under strip loading were investigated.The results show that during the settlement of strip footing,horizontal displacement accumulates firstly in the unreinforced zone near the lower right and left corner of the reinforced zone,and then extends upward to reinforcement layers,which causes the tensile failure of the reinforcements successively from bottom to top and at last forms macro shear failure surface.Two stress diffusion zones are formed during the settlement of the strip footing.The two zones extend downward along the bend section of each reinforcement layers and the trip footing edges,respectively.The stress diffusion angle along the bend section is 2.5 times of that along the strip footing edges.Both of reinforced and unreinforced foundations fail in Prandtl slide mode.The depth and width of the slip surfaces increase with an increase of reinforced depth and reinforcement length.