Grit refers to the passion and persistence towards long-term goals and it is the most reliable trait to predict one's future success. Therefore, the research of grit quality among teenagers, including relevant factors and models, has significant practical value. The current study conducted a survey to 880 students at a high school in Gansu Province, including grit scale, the scale for parental rearing style, hope scale, and the scale for clarity of self-concept. The survey also collected each student's demographic information. A total of 850 valid responses have been collected, and SPSS 24.0 was taken for data analysis. A variety of analytic methods were used in this study, including analysis of variance of grit among demographical variables, Harman's Single Factor Test for Common Method Bias, Pearson's Correlation, regression analysis, and Process Marcoes for SPSS for mediating analysis, moderating analysis and moderated mediating analysis. The conclusion is that positive parental rearing styles can promote grit among high-school students, which is partially achieved by improving their sense of hope. Meanwhile, clarity of self-concept contributes to the increase of grit by parental rearing style through enhancing the sense of hope. This moderated mediation model can provide specific suggestions and guidelines for developing teenagers' grit. Also, this model can be used in conjunction with intellectual tools such as high-school students' profiles, personalized analysis, and accurate recommendations to help promote the development of grit.