Self-assembled In0.4Ga0.6As island arrays have been grown on (311)B GaAs substrates by using atomic hydrogen-assisted molecular beam epitaxy (H-MBE). The evolution process of surface morphology with deposition has been analyzed by atomic force microscopy (AFM) and the development of lateral ordering has been highlighted by two-dimensional fast Fourier transformation (2DFFT) analysis of the AFM images. It is revealed that the InGaAs islands are arranged in nearly perfect two-dimensional (2D) square-like lattice with two sides parallel to [01 - 1] and [- 2 3 3] azimuths. Such an alignment of islands is coincident with the anisotropy of bulk elastic modulus of the GaAs (3 1 1)B substrate.