ordinary ceramic particles not coated ordinary quartz sand not coated and the coated quartz sand prepared in the examples 1 u02dc 16 in the present invention in volume of 40 ml each and load them into test tubes of the same size respectively add 20 ml water colorless liquid and kerosene yellow liquid into the test tubes respectively and judge the oil water permeability of the liquids by observing the permeation state in the liquids the result is shown in table 1 it could be seen from table 1 oil and water permeate quickly through ceramic particles and quartz sand in contrast they permeate much slower in the coated quartz sand according to the present invention and the permeated volume is much loss the residual volume of water above the coated quartz sand is the greatest and the water level is higher than the kerosene level by 7 ml or more thus it is proved that the coated quartz sand prepared in the present invention has poor hydrophilicity and has water retardant function in static state weigh 50 g coated quartz sand prepared in example 1 pour the coated quartz sand into the rubber packer of a core holding unit apply 4 0 mpa confining pressure and displace clean water.