Using diatomatomite as siliceous raw materials,tobermorite with lamellar structure was synthesized by dynamic hydrothermal method.In addition,the influences of the aluminum content in the raw materials and the sodium dodecyl sulfate（SDS） on the morphology of the products were investigated.The results showed that under the conditions of synthesis tempera-ture of 200 ℃,time of 6 h,liquid-solid ratio of 20 mL/g,SDS addition amount of 2.4% and stirring speed of 160 r/min,the tobermorite product with good lamellar structure was prepared. Based on the comparative experiments using pure SiO₂ as the silicon source,it was found that aluminum impurities in the diatomite was one of the main factors for the formation of flakye tobermorite.The substitution of aluminum atoms for silicon atoms in bridged tetrahedra prevented the formation of silicon-oxygen tetrahedron double chained and promoted the growth of crystals into plate-like crystal forms.On the other hand,the sodium dodecyl sulfate,as an anionic surfactant,could bond with the H—O on the（001） crystal plane of tobermorite,hinder-ing the growth of crystals on the（001） crystal plane and promoting the growth of flaky crystal form as well.