A new kind of polarization maintaining photonic crystal fiber with two side-holes is designed. There is only a layer of small air holes between the core and the large air hole， and two large air holes are introduced in the cladding symmetrically. The two-dimensional model was simplified by the plane strain hypothesis， the two-dimensional model of this fiber was numerically analyzed by the finite element method， and the characteristics of temperature and hydrostatic pressure sensing were studied by calculating the birefringence-induced frequency shift at different temperatures and hydrostatic pressures. As the studies show， within a large range of hydrostatic pressure and temperature， this polarization maintaining photonic crystal fiber can realize the hydrostatic pressure sensitivity of -2.135 3 GHz/MPa and it is insensitive to temperature without doping any stress material. Its temperature sensitivity is only +0.154 2 MHz/℃. In addition， the optical properties of the photonic crystal fiber were also analyzed. The proposed photonic crystal fiber satisfies the condition of single-mode transmission， has a small confinement loss and a large effective mode area. Due to its characteristics of small size， strong compatibility with other optical fibers， high hydrostatic pressure sensitivity and temperature insensitivity， it has obvious advantages in the accurate measurement of hydrostatic pressure in the environment with variable temperature and great hydrostatic pressure variation. Better optical properties make it has important reference value in monitoring application of oil well and civil engineering.