Objective To explore the interaction and influence paths among the emotional intelligence, shared decision-making competency and nurse-patient relationship among psychiatric nurses, and to provide new ideas for the subsequent implementation of shared decision-making and the intervention of nurse-patient relationship. Methods A total of 675 psychiatric nurses from eight specialized psychiatric hospitals in Chengdu were selected, then they were investigated by using a general information questionnaire, the Self-rating Scale for Competency of Shared Decision-making in Nursing Staff, the Emotional Intelligence Scale, and the Nurse-Patient Relationship Scale based on the Nurse′s Perspective. Structural equation modeling was used to examine the mediating effect of psychiatric nurses′ shared decision-making competency on emotional intelligence and nurse-patient relationships. Results The participants had a total score of emotional intelligence (82.16±15.25), shared decision-making competency (186.08±34.12), and nurse-patient relationship (43.72±7.89). Emotional intelligence was positively correlated with shared decision-making competency and nurse-patient relationship, and shared decision-making competency was positively correlated with nurse-patient relationship (all P<0.05). Psychiatric nurses′ shared decision-making competency partially mediated between emotional intelligence and nurse-patient relationship, with a mediation effect value of 0.171, and the indirect effect accounted for 29.53% of the total effect. Conclusion Psychiatric nurses′ emotional intelligence, shared decision-making competency, and nurse-patient relationship are at a medium and above level; shared decision-making competency is a mediating variable between emotional intelligence and nurse-patient relationship. Nursing administrators should strengthen the education and training of psychiatric nurses′ emotional intelligence and shared decision-making, and improve nurses′ shared decision-making competency, so as to promote the development of a good nurse-patient relationship.