InGaN quantum dots were grown on sapphire substrate by radio-frequency plasma-excited molecular beam epitaxy (RF-MBE). The effects of InN nuclear layer on the structural and optical characteristics of InGaN quantum dots were studied. In-situ reflection high energy electron diffraction (RHEED) was used to analyze the growth of the InGaN dots structures. Atomic force microscope (AFM) and photoluminescence (PL) were used to characterize the structure and optical properties of the InGaN quantum dots. The results show that the InGaN quantum dots grown on the InN nuclear layer can get higher density and better quality compared with that grown directly on GaN layer. The sizes of InGaN quantum dots grown on the InN nuclear layer are more uniform, about 35-45 nm and the density can reach 3.2 × 1010/cm2. The PL intensity of the InGaN quantum dots grown on the InN nuclear layer is twice as high as that of the InGaN quantum dots grown directly on GaN layer. The FWHM of the quantum dots PL peak is about 10 nm