Despite persistent efforts in untangling the mechanism of scientists switching between research topics, little is investigated for the relationship of scholars’ career stage switch leading to dynamics of research topics. In this paper, aiming to reveal career stage and its influence on research topics, we construct a two-layer network model, coauthors collaboration network ($\alpha$-layer) for scholars research career stages and papers similarity network ($\beta$-layer) for research topic types, and analyze the relationship between the career stage switch and the topic type change. Applying the data set SMSEC from China to the model, the different statistics of the two layers show different forming mechanisms, the preference attachment and the rule of similarity inherited in the two layers, respectively. The coupling mechanism of the two layers is displayed by correlation of career stages and topic types, and presented by a framework with contributions of new added papers and associated scholars. The results show that the longer of research career is, the bigger contribution on the type of divided topics is; a scholar with large topic scopes would more likely insist in his/her research.