Semiconductor silicon nanoparticles have many novel electromagnetic properties and have became a research hotspot in optoelectronics in recent years. In order to improve the luminescence intensity of Quantum Dot（QD） photoluminescence devices

a dimer composed of two silicon nano-cubes of different sizes is proposed. By the Finite Difference Time Domain（FDTD） method

the luminescence enhancement of QD by silicon nano-dimers is studied in terms of fluorescence excitation rate enhancement and quantum yield enhancement. The results show that the dimer composed of two silicon cubes with different sizes can enhance the luminescence of CdSe QDs. When the side length of the two silicon nano-cubes and the gap between them getting smaller

the fluorescence excitation rate enhancement factor and the quantum yield enhancement factor of the QDs tend to increase gradually. In particular

when the side lengths of two silicon nano-cubes are 100 nm and the gap of the silicon dimer is 20 nm

the structure of silicon nano-dimer is optimal

and the fluorescence intensity of CdSe QDs can be enhanced by about 24 times.