A new type of optimized Photonic Crystal Fiber(PCF) with high birefringence and high nonlinearity was proposed by adjusting its structure parameters. The cladding of the PCF was arrayed by circular air holes of different sizes in accordance with the hexagonal lattice and two ellipse air holes were guided to its fiber core centre along the x axis. By using the full vector finite element method with anisotropic perfectly matched layers, the mode field distribution, effective index, effective mode area, nonlinearity and birefringence and the fiber structure were investigated simultaneously and the effects of different optical parameters on the optical characteristics were analyzed. The analysis shows that the birefringence and nonlinearity properties can be controlled by adjusting the sizes of large air holes and ellipse air holes. The numerical results indicate that a better result can be obtained when the parameters of the PCF are adjusted appropriately.The maximum nonlinear coefficient of 53.5 W-1·km-1 and high birefringence of 1.092 9×10-2 are obtained at 1.55 μm, in which the birefringence is two orders of magnitude higher than that of the traditional optical fiber. The modified fiber has a wide application prospect in the communication system that needs high nonlinear and high birefringence.