The　main　influencing　factors　of　the　stability　of　growth　system　of　tetragonal　potassium　dideuterium　phosphate　(DKDP)　crystal,　such　as　the　deuterium　content　in　solution,　the　purity　of　the　solution,　saturation　temperature,　rotative　velocity　of　crystal,　the　superheating　temperature　and　period,　the　homogeneity　of　growth,　the　stress　on　the　crystal　from　outside　and　the　size　of　the　seed　crystal,　have　been　studied　and　analyzed　from　the　viewpoint　of　thermodynamics　and　kinetics.　It　is　indicated　that　the　metastable　zone　of　tetragonal　DKDP　crystal　growth　can　be　widened　and　the　starting　temperature　of　crystal　growth　can　be　raised　to　50°C　by　using　high　purity　raw　materials,　super　fineness　filtering　(bore　diameter　0.15μm)　and　superheating　at　10°C　higher　than　the　saturation　point　for　20　h,　so　the　rapid　growth　of　DKDP　crystal　in　all　directions　can　be　realized　at　the　conditions　of　lower　acidity　and　higher　supersaturability.