Micro-nano materials, products obtained by covalently modifying the surfaces of micro/nano materials with hydrophilic materials, and methods for making the same. The micro/nano materials on the surfaces have carboxyl groups or/and pro-carboxyl groups which are converted into their active esters. The products are covalently modified by forming amide bonds between the active esters on the surfaces and the modification agents; where the modification agents are hydrophilic compounds and/or hydrophilic polymers bearing primary and/or secondary aliphatic amines. Monomers bearing carboxyl groups and/or pro-carboxyl groups are used to produce an adequate number of carboxyl groups and/or pro-carboxyl groups on the surface of a polymer material to be modified. The carboxyl groups and/or pro-carboxyl groups are converted into active esters. A reasonably-sized modification agent bearing primary and/or secondary amines, zwitterions and hydrophilic linear spacer arms is used to form amide bonds and obtain a covalently modified surface layer.