For improving the nonlinearity and dispersion properties of nan-core fiber, the idea of enlarging the nonlinearity and improving the dispersion characteristics of the present nano-core fiber by nonlinear fluid filling method is proposed. The special impact of selective fluid filling method on the fiber nonlinearity and dispersion is analyzed too. Calculation results show that the appropriate structure parameters and the specific selective filling method could help to enhance the nonlinearity and improve the fiber dispersion characteristics.