A new pentagon polarization maintaining photonic crystal fibre with low nonlinearity is introduced.The full vector finite element method was used to investigate the distribution and the effective area of modal field,the nonlinear properties,the effective indices of two orthogonal polarization modes and the birefringence of the new PM-PCF effectively.It is found that the birefringence of the new polarization maintaining photonic crystal fibre can easily achieve the order of 10～(-4),and it can obtain higher birefringence,larger effectively mode-field area and lower nonlinearity than traditional hexagonal polarization maintaining photonic crystal fibre with the same hole pitch,same hole diameter,and same ring number.It is important for sensing and communication applications,especially has potential application for fibre optical gyroscope. A new pentagon polarization supported photonic crystal fiber with low nonlinearity is introduced. The full vector finite element method was used to investigate the distribution and the effective area of ​​modal field, the nonlinear properties, the effective indices of two orthogonal polarization modes and the birefringence of the new PM-PCF effectively. I found that the birefringence of the new polarization held photonic crystal fiber can easily achieve the order of 10 ~ (-4), and it can obtain higher birefringence, greater effective mode-field area and lower nonlinearity than traditional hexagonal polarization holding photonic crystal fiber with the same hole pitch, same hole diameter, and same ring number. It is important for sensing and communication applications, especially has potential application for fiber optical gyroscope.