KTP crystals with sizes up to 24mm×60mm×14mm(a×b×c)were grown by hydrothermal method using a solution of K_2HPO_4、KH_2PO_4、H_2O_2 as mineralizer,and crushed flux KTP crystals as nutrients.The crystal morphorlogy,the crystal habit and especially the reason of forming the high index face under the hydrothermal condition were studied.