Objective To explore the self-management behavior intention of pregnant women with gestational diabetes mellitus（GDM）based on the theory of planned behavior,and to provide a basis for promoting good self-management during pregnancy. Methods Using the phenomenological research method in qualitative research,12 pregnant women with GDM were interviewed in an in-depth semi-structured interview,and then the themes were summarized by Colaizzi's seven-step content analysis. Results According to the theory of planned behavior,the themes were summarized into three categories and eight themes including（1）Behavioral Attitudes：cognition deficiency,positive attitude,and negative attitude,（2）Subjective norms：family influence,medical pressure,interpersonal pressure,and（3）Perceptual behavior control：self-management knowledge acquisition limitations,self-management Objective conditions constraint. Conclusions Most of the respondents have insufficient awareness of self-management of gestational diabetes,different patients have different attitudes towards self-management,and self-management behavior is affected by external pressures such as family,medical staff,and interpersonal relationships,and there are many obstacles due to a lack of knowledge and skills,Objective conditions．Medical staff should strengthen the self-management education of pregnant women with gestational diabetes,provide timely support,and improve their self-management efficiency．