The formation process of CdSe self-assembled quantum dots (SAQDs) was investigated systematically by atomic force microscopy (AFM). Several monolayers (MLs) of CdSe coverage were grown directly on GaAs substrates by metalorganic chemical vapor deposition (MOCVD). AFM images were taken constantly on the same area within several hours after the growth. It revealed that the relaxation of misfit strain is completed by two competing processes. One is the formation of quantum dots assisted by surface diffusions another is the formation of misfit dislocations.