Solubility　curves　of　KDP　(KH2PO4)　in　solutions　with　different　pH　values　were　measured.　It　was　found　that　the　solubility　of　KDP　crystal　increased　with　the　reduction　pH　value　of　solution.　Transparent　KDP　crystal　was　grown　from　solution　with　1.5　pH　by　point　seed.　Chemical　etching　experiments　revealed　that　pyramid　sector　of　the　crystal　displayed　more　growth　defects.　Growth　defects,　such　as　growth　striation　and　inclusion,　were　analyzed　by　white-beam　synchrotron　radiation　X-ray　topography.　The　reasons　for　the　formation　of　these　growth　defects　were　discussed.　Transmittance　spectra　test　of　both　prismatic　sector　and　pyramidal　sector　was　performed.　©　2009　WILEY-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinhei.