Abstract: The dynamic fracture toughness of X70 pipeline steel were measured at different temperatures. It was found that loading rate was important as temperature to dynamic fracture toughness. At constant temperature, increasing loading rate can induce the fracture transition from ductile to brittle. It causes fracture transition when decreasing temperature from 298 K to 193 K and increasing loading rate from 0.01 mm/s to 1 000 mm/s.