Abstract: Single-and Multi-layer InAs quantum dots grown on (001) GaAs substrates by molecular beam epitaxy (MBE) were studied by transmission electron diffraction (TEM) and the structural properties of the quantum dots were discussed. The results indicated that multi-layer quantum dots are aligned vertically, in addition, the density of the dots decreases and the size of dots becomes uniform when the number of layers increases.In this experiments, the thickness of InAs dots sheets and GaAs space layers in samples with five dots sheets are the best condition to form the strain field needed by growth of self-organized quantum dots.