Abstract: [Purpose/Significance] This paper focuses on the influencing factors of the users paying to view existing answers in the paid Q&A communities , to help understand the psychology of users to pay for existing answers and the behavior patterns of answers and questioners, optimize the product design of community operators. [Design/Methodology] Drawing on the information foraging theory and related literature, we proposed a model and hypotheses.Using 14,167 samples from the three fields of health care, finance and Internet information in Weibo Q&A, and generalized linear regression method（GLM）, we verified the influence mechanism of each factor on users' payment for existing answers. [Findings/Conclusion] The question price and the level of detail of the question have a positive impact on the number of viewership of existing answers; there are more viewership on questions in the field of Internet information than viewership on questions in the fields of health care and finance, but the average number of questions answered by answerers in the field of Internet information is less than that in the other two fields; The likability of the answerers in the health care field does not positively affect the number of viewership; the emotions reflected in the question description is important in the field of health care, positive emotions positively affect the number of viewership, and negative emotions negatively affect the number of viewership. [Originality/Value] Our findings enrich current research about the influence of question characteristics（including emotion characteristics and question types）on users' payment for existing answers, and provide reference for designing paid Q&A products.

Key words: Knowledge payment, Payment for existing answers, Q&A communities, Information foraging theory