Low-energy electron diffraction(LEED) and scanning tunneling microscopy(STM) have been used to determine the adsorption structures of glycine on the Cu(001) surface at room temperature.Glycine can adsorb on Cu(001) to form three ordered structures:one c(2×4) and two of the type of (2×4) structures,i.e.,(2×4)1 and (2×4)2.According to the molecular resolution STM images and the rule about missing spots in LEED,it is deduced that the carboxylic groups of the two molecules in a unit cell of any of the two (2×4) structures have the same adsorption geometry with respect to the substrate,while the amino groups do not.The three adsorption structures are expected to have almost the same energy,as the narrow stripped domains of them may co-exist and the c(2×4) and (2×4)2 domains sometimes may even change from one to another.