The relation between the failure pressure of pipeline with irregular-shaped defect and the characteristic geometric parameters is more complex than regular-shaped defect. Therefore, it is necessary to study the evaluation method of failure pressure of pipeline with irregular-shaped defect. The failure pressure of pipeline with irregular-shaped defect is mainly determined by the evaluation range and the irregularity, which is defined as the ratio of the maximum value to the average value of defect depth. In order to improve the efficiency of failure pressure assessment and the accuracy of prediction results of pipeline with irregular-shaped defect, the paper presents a case study on the failure pressure of irregular-shaped defect using solid Finite Element models. The case is composed of shallow patch and deep defect and the deep defect are included in the shallow patch. The effect of the length and depth deep defects on the failure pressure of pipeline with irregular-shaped defect are analyzed. According to the evaluation scope and defect length of irregular defects, the calculation model of evaluation length is proposed. Case 1 and case 2 are composed of a shallow defect and one deep defect, which are used to analyze the relationship between failure pressure and irregularity of the defect. Case 1 is used to analyze the influence of the length of deep defect on the failure pressure, and case 2 is used to analyze the influence of the depth of deep defect on the failure pressure. According to the irregularity of the depth profile, the defect is divided into three categories:the irregularity of the first type of defects is 1≤d/dave＜1.2, and the axial projection shape of this type of defects can be equivalent to a parabola, The irregularity of the second type of defect is 1.2≤d/dave≤1.5, the axial projection shape of this type of defects can be equivalent to a rectangle, and the irregularity of the third type of defects is 1.5＜d/dave. The equivalent shape of the axial projection of this type of defect is between rectangle and parabola. According to the equivalent shape of the defect with different irregularity, the value model of the effective depth of the defect is obtained. Combined with the effective depth of equivalent shape and the evaluation length, a new method is proposed for predicting failure pressure of steel pipeline with irregular-shaped defect by improving the DNV-RP-F101 criterion. Firstly, according to the length of the irregular-shaped defect, the evaluation length is determined. Then the effective depth of the defect is determined by combining the depth ratio of deep and shallow defects. Finally, the evaluation length and effective depth are introduced into the failure pressure calculation formula to evaluate the failure pressure. The predictions of burst capacity with the new method of the pipeline with irregular-shaped defect are in good agreement with experimental results for different steel grades. The average error of the method proposed in this paper is only 1.69%. Compared with the effective area method with the smallest error in the existing evaluation methods, the error is reduced by 86.37%