Using　3-mercaptopropyl　trimethoxysilane(MPTS),　3-aminopropyl　triethoxysilane(APTES)　and　citric　acid　(CA)　as　raw　materials,　the　surface　modified　diatomite　with　mercapto　(-SH)　and　amino/carboxyl　(-NH2/-COOH)　was　prepared　by　water　bath　method　and　water　bath/low　temperature　hydrothermal　method,　respectively.　The　samples　were　characterized　by　Fourier　transform　infrared　spectroscopy,　scanning　electron　microscope,　N-2　adsorption-desorption　measurement,　thermogravimetric　analysis/differential　scanning　calorimetry,　X-ray　photoelectron　spectroscopy　and　other　technologies,　and　the　preparation　mechanism　was　discussed.　When　the　pH　value　of　heavy　metal　ion　solution　was　7　and　the　adsorption　time　was　4　h,　the　diatomite　sample　modified　by　MPTS　showed　the　maximum　adsorption　capacities　of　396　and　365　mg.g(-1)　towards　Pb(II)　and　Cd(II),　respectively,　and　the　diatomite　sample　modified　by　APTES　and　CA　showed　the　maximum　adsorption　capacities　of　485　and　462　mg.g(-1)　towards　Pb(II)　and　Cd(II),　respectively.