Abstract: The high-temperature mechanical properties of offshore platform continuous casting steel slabs E690 were tested on thermal stress-thermal simulation device (Gleeble-3800) and the high-temperature strength curve and high-temperature ductility curve from 600 ℃ to 1 350 ℃ was obtained. Results show that with the increase of stretching temperature, the tensile strength of the experimental samples decreases; the high -temperature ductility becomes better, and the high ductility region gets wider. A ductility trough is observed between 800 ℃ and 950 ℃ which is the third brittle zone. Metalloscope and scanning electron microscope were used to observe the situation of brittle fracture. The results show that transgranular fracture dominates below 1 300 ℃, while melting fracture dominates with the temperature from 1 300~1350 ℃, which means that the high ductility region is wide and the high-temperature plastic is fine.