Objective To investigate the influence of stress on insomnia among plateau soldiers,and explore the mediating role of parent-child alienation and the moderating role of emotion regulation strategies in this relationship.Methods A cross-sectional study design was adopted in this study.Our Self-designed General Information Questionnaire,Plateau Soldiers Stressor Scale,Insomnia Severity Index,Inventory of Alienation towards Parents,and Emotion Regulation Scale were employed to survey 2 065 plateau soldiers at an average altitude of 4 200 m.With aid of SPSS 26.0 statistics,descriptive analysis,correlation analysis and regression analysis were applied to analyze stress status,parent-child alienation,insomnia and emotion regulation in the participants,and then a structural equation model was established.Results ① The scores of stress,parent-child alienation and insomnia were significantly higher in the participants who were older,well educated(P＜0.01)and were or had been in a marital relationship(married,divorced,or widowed)(P＜0.001)than those without above conditions.② Significant pairwise positive correlations were observed among stress,parent-child alienation,insomnia,cognitive reappraisal,and expressive suppression(r=0.08～0.61,P＜0.001).③ Stress and expressive suppression could positively predict parent-child alienation(β=0.14～0.43,P＜0.001),and stress,parent-child alienation and expressive suppression could positively predict insomnia(β=0.04～0.25,P＜0.01).Cognitive reappraisal could not significantly predict parent-child alienation or insomnia.④ Parent-child alienation towards parents partially mediated the relationship between stress and insomnia,with a mediation effect accounting for 7.29％of the total effect.⑤ Expressive suppression moderated the impact of stress on insomnia(β=-0.01,P＜0.001),and the higher expressive suppression level mitigated the adverse effect of stress on insomnia when compared with the lower expressive suppression level.Conclusion For plateau soldiers,stress significantly predicts insomnia,with parent-child alienation playing a mediating role.Furthermore,a higher level of expressive suppression can effectively buffer the influence of stress on insomnia.