Abstract: Isothermal double tension tests were carried out on EH40 and EH47 steel plates with thickness of 85 mm and 90 mm for large container ships. Test parameters were determined according to maximum design stress and temperatures under specified crack arrest toughness values to confirm the validity of crack arrest toughness index (-10℃ and K_ca ≥ 8 000 N/mm^3/2 for plates thicker than 80 mm).Resultsshowed that for tested plates with K_ca=8 000 N/mm^3/2 at-10℃, crack arrest occured, indicating the validity of the index value.