In order to study the fracture behaviour of hydroxyl-terminated polybutadiene (HTPB) propellant, the low temperature fracture toughness experiment of HTPB propellant was carried out by using centrally cracked sheet tensile specimens. The fracture toughness values of HTPB propellant with mode I crack at different temperature and loading rate were obtained, and the effect of specimen thickness on the fracture toughness was investigated. The experimental results show that the fracture toughness value continuously increases with the decreasing of temperature and the increasing of loading rate, and a linear relationship exists between the fracture toughness and the logarithm of loading rate. The effect on the fracture toughness by the change in loading rate is more notable at a lower temperature. Both at 25 degrees C and -40 degrees C, the fracture toughness of thick specimens is higher than that of thin specimens, and at low temperature the change is more obvious. A master curve of quadratic function for the fracture toughness was obtained. The influence of temperature on the fracture toughness is more obvious than that of the strain rate with double factor analysis of variance.