Objective To analyze the psychometric performance of Experiences in Close Relationships Inventory (ECR) for medical undergraduates in Guangdong. Methods Stratified random sampling method was used to select 855 medical undergraduates from 7 colleges in Guangdong, and ECR was used to investigate them. Cronbach's α coefficient and split-half reliability were used to analyze the internal consistency of the questionnaire. Convergent validity, discriminant validity, and factor analysis were used to evaluate its structural validity. Celling and floor effects were used to evaluate its sensitivity. Results Cronbach's α coefficients of the total questionniar, attachment anxiety, and avoidance were 0.822, 0.721, and 0.687 respectively, which met with the requirements of the group comparison. Spearman-Brown split-half coefficients of the total questionniar, attachment anxiety, and avoidance were 0.829, 0.715, and 0.741, respectively. The calibration success rate of convergent validity of attachment anxiety and avoidance were 88.89% and 94.44%, respectively. The calibration success rate of discriminant validity of attachment anxiety and avoidance were both 100%. Two components obtained from 36 items, with a cumulative variance contribution rate of 42.888%, which basically met the theoretical conception of ECR. The scores of attachment anxiety and avoidance were governed by the normal distribution, without any floor or celling effect. Conclusions The psychometric performance of ECR for medical undergraduates in Guangdong was valid and reliable.