By　observing　the　{100}　faces　morphology　of　DKDP　crystal　grown　in　all　three　dimensions　with　atom　force　microscope,　screw　dislocations　were　found.　So　it　is　deducted　that　the　crystal　growth　on　the　{100}　face　complies　with　screw　dislocation　mechanism.　The　defects　in　the　crystals　were　observed　and　analyzed　by　synchrotron　radiation　X-ray　white-beam　topography.　And　the　influences　of　various　growth　conditions　and　stages　on　the　perfection　of　growing　DKDP　crystal　are　approached.