Age-related differences in personality have captured human attention for centuries. For instance. Developmentally oriented research has painted a picture of both stability and change in personality traits across the life span. Nonetheless, there are still some questions about the development of core personality dispositions like those captured by the Big Five domains, such as the universality and particularity of personality development. In this article, we pursue a partial answer to this question by testing for age-related differences in mean levels of the Big Five traits in a nationally representative cross-sectional sample of Chinese. These analyses are particularly informative given that very few studies have examined age differences in representative samples that cover substantial periods of the life span. In addition, we examine age differences in specific personality adjectives linked to the Big Five to identify whether narrower aspects of personality show similar patterns of age differences as do their respective Big Five traits. This study used cross-sectional investigation method to determine the patterns of mean-level change in Chinese big five personality traits across the life course. In this study, Cross-sectional age differences in the Big Five personality traits were examined in a nationally representative sample of Chinese (N =3426; ages range from 15 to 75). We further analyzed the patterns of mean-level change in Chinese big five personality traits and 10 specific facet traits across the life course. The results of the study showed that for people under the age of 60, the older individuals had lower mean-level of neuroticism, however, for people aged 60 or older, the older individuals had higher mean-level of neuroticism; for people under the age of 50, the older individuals had lower mean-level of extraversion, however, for people aged 60 or older, the older individuals had higher mean-level of extraversion; on the whole, the older individuals had lower mean-level of openness; on the whole, the older individuals had higher mean-level of agreeableness; and on the whole, the older individuals had higher mean-level of conscientiousness. On the whole, the middle-aged adults had higher mean-level of conscientiousness, agreeableness and extraversion than young adulthood and old people; and the middle-aged adults had lower mean-level of neuroticism and openness than young adulthood and old people. Correlation analysis results show that age was negatively related with mean levels of neuroticism, anxiety, depression, activity, openness to experience, aesthetics and ideas, and positively related with mean levels of extraversion, assertiveness, altruism, compliance, order and self-discipline. There were significant main effect of gender on mean levels of big five personality traits. Such as man had lower mean-level of neuroticism than woman; and men over the age of 50 have higher mean-level of Conscientiousness than y woman over the age of 50. In conclusion, the present research comprehensive analyzed the development trajectories of Chinese big five personality. It contributes to our understanding of the patterns of mean-level change in Chinese big five personality traits across the life course. These findings provide an important step in the classification and understanding of the development trajectories of Chinese big five personality traits. And these results also provide some empirical evidences sinicization research and cross-cultural comparison.