In order to study the mechanical properties and failure mechanism of the solid propellant under extreme low temperature environment, the uniaxial tensile test of a three-component butyl hydroxyl propellant was carried out under different temperatures, wide range of superimposed pressure values and high strain rate conditions by adopting the self-developed wide-temperature-superimposed pressure loading test system, and the fracture morphology was observed by electron microscope scanning. The effect of temperature, tensile rate and peripheral pressure value on the mechanical properties of the propellant was analysed, and the damage mechanism of the propellant under different working conditions was discussed. Results show that when the tensile rate increases, the superimposed pressure increases and the temperature decreases, the elongation of the dewetting point of the propellant decreases, the dewetting point moves forward, and dewetting occurs inside the propellant. There are superimposed pressure and strain rate thresholds, above which the propellant is more prone to dewetting behaviour. At low temperature, the maximum elongation of propellant is more sensitive to the change of high tensile rate, and its maximum tensile strength and maximum elongation both tend to increase with the increase of the value of the peripheral pressure, and the maximum elongation is 28.8% under the extreme tensile condition of -55 ℃, 10 MPa, and 4 200 mm/min. The failure mode of the propellant is affected by a combination of dewetting damage, matrix fracture, and particle cracking, as the temperature decreases and the tensile rate increases.