Abstract: Based on the analysis of crack arrest behavior with principle of conservation of energy,the relationship between crack arrest temperature measured by temperature-gradient double tension test and stress,plate thickness and impact toughness measured with sample surface at -40 ℃ was studied with 52 groups of test data of low alloy steel plates. The crack arrest temperature formula was founded as T_k=-66.1+0.011 8·(σ·t²/KV₂)。.