The author reported in his previous paper that almost continuous stop and go process of small crack extension was observed on the notched specimen with structural steel during unloading stage of the compression load which had been applied to a certain value at-196°C. In the present paper these cracking phenomena were investigated theoretically. The state of the plastic zone spread and that of the crack initiation from the initial crack were expressed using the Dugdale model. This equation determines the crack extension length as a function of the applied stress by adopting the ω⁺ (plastic zone length under tension yield stress) concept as a fracture initiation criterion. Through the judgement of the stability of the state that is expressed by this equation, the relation between precompression stress and the final fracture stress was obtained. For the convenience of the practical use, approximate equations of the analytically derived equation for a crack in an infinite plate were proposed. These theoretically derived relations were compared with those obtained through experiments and showed a fair agreement with each other.