Affective diathesis is relatively stable and positive as an affective mental characteristic, it consists of six factors, moral affection, rational affection, aesthetic affection, interpersonal affection, life affection, and emotional intelligence. Affective diathesis is considered as the basic component of individual’s mental diathesis, and plays a fundamental role in boosting students’ overall development. The affective diathesis of students at different level of education may possess unique characteristics such that it is worthwhile to explore the uniqueness of the affective diathesis for different student cohorts. Meanwhile, Graduate education is an important source of blue-ribbon talents, so the study of the affective diathesis of graduate merits attention. But the existing literatures pertinent to graduate students were focused on their research ability and creativity, few has investigated the affective diathesis. They found that (1) the overall affective diathesis of the participants is relatively good, (2) among the six factors, the overall life affection and moral affection of the participants were at a relatively high level whereas the overall interpersonal affection, aesthetic affection, and emotional intelligence were at a relatively low level. But more fine-grained analysis should be done to provide a window into the affective diathesis from a person-oriented perspective, for example, whether the graduate students cohort could be categorized into different groups based on their affective diathesis, if so, what are the inter-group differences of affective diathesis. Therefore, this study applied latent class analysis (LCA) to classify students into different latent groups based on their response pattern in the “Questionnaire on College Students’ Affective Diathesis”. Data were collected on a sample of 10056 graduate students from 51 universities in 14 cities (such as Beijing, Shanghai, Nanjing, Guangzhou, Changchun, Zhengzhou, Xi'an, Wuhan, Xining, Lanzhou, Guiyang, Nanning, Haikou, Kunming, and so on) in China. Based on the LCA results, this study (1) explored the inter-group characteristics of affective diathesis and (2) determined appropriate cutoff values for the “Questionnaire on College Students’ Affective Diathesis”. Results shown that the overall affective diathesis of graduate is good, but there are differences in the developmental level. What’s more, the development law of the internal dimension of affective diathesis is not consistent. More specifically, the development of the affective diathesis of graduate students can be divided into three levels: excellent, good and in general. In the excellent level, the development of moral emotion, rational emotion, life emotion, aesthetic emotion and interpersonal emotion is better than the emotional intelligence, while the general level is the opposite, and the development of the good level is more balanced in each dimension. Further analysis shows that gender and major both have an effect on the development of affective diathesis. In addition, based on the results of LCA, the present study set cut-off values for the “Questionnaire on College Students’ Affective Diathesis” to classify students into different categories according to their observed total score. If one’s score is higher than 858, he/she would be classified as belonging to the better group, if one’s score is below 720, he/she would be classified as belonging to the need-to-be-improved group, if one’s score is between 858 and 720, he/she would be classified as belonging to the good group.