Meandering and triangular macrostep trains on (1 1 1) surface of diamond single crystals grown from Fe-Ni-C system under high-pressure and high-temperature (HPHT) were for the first time systemically revealed by atomic force microscopy (AFM). The height of macrosteps is in a range from 10 to 26 nm. which about several tens times unit cell parameter of diamond single crystal. The formation mechanism of the meandering and triangular macrosteps was discussed through consideration of adsorbed impurity on the growing step, the interlay between step energetics (repulsive step interaction) and kinetics (asymmetric step kinetics) on the growing diamond crystal surface. (C) 2002 Published by Elsevier Science B.V.