Objective: To explore the value of vector angle of Lorenz plots(LPs) and the role of combining B-line slope in improving the diagnostic efficiency of arrhythmia． Methods: LPs of 119 cases with ventricular premature contraction (VPC group ) ，97 cases with supraventricular premature contraction(SPC group) ，52 cases with type II°I atrioventricular block ( Ⅱ ° Ⅰ group) and 54 cases with type Ⅱ ° Ⅱ atrioventricular / sinoatrial block ( Ⅱ ° Ⅱ group) were retrospectively analyzed．The B-line slope and vector angle were measured，and the differences between groups were compared. Receiver operating characteristic curve was used to analyze the diagnostic efficacy of B-line slope，vector angle and their combination between groups ，and MedCalc software was used for statistical comparison．The consistency of intra-observer and inter-observer measurements of B-line slope and vector angle was evaluated using Intra group correlation coefficient (ICC) and Bland-Altman plot. Results: There were significant differences between VPC group and SPC group，and between Ⅱ ° Ⅰ group and II°II group (P＜0. 05) ．The area under the curve (AUC) of B-line slope，vector angle，and the combination of the two in distinguishing ventricular and supraventricular premature contraction were 0. 81，0. 84 and 0. 87 respectively，and the AUC in distinguishing type Ⅱ ° Ⅰ and type Ⅱ ° Ⅱ atrioventricular / sinoatrial block were 0. 76，0. 78 and 0. 80 respectively．The ICC of vector angle was better than B-line slope (Intra-observer 0. 99 vs 0. 98，Inter-observer 0. 97 vs 0. 96) ． Conclusion Vector angle can be used to identify the type of arrhythmia，and has good intraobserver and interobserver consistency．Its combination with B-line slope has the highest accuracy in diagnosing arrhythmia，providing a new reference for clinical diagnosis and treatment.