In the era of smart media, exploring the development of paid news business is a useful direction for newspaper media groups to improve the quality of news and operation level, and this paper argues that clarifying and balancing the relationship between free content and paid content is the key to the development of paid business. This paper puts this issue into the framework of the biological theory of “symbiosis”. Firstly, the symbiotic logic of paid news and free content is explained from the three levels of responsibility function, content form, and competition relationship. Secondly, taking the development history of paywalls as an example, we summarize the transformation process of the symbiotic relationship between paid and free content from commensalism to mutualism, and generalize the reverse evolution and spiral evolution modes from it. Finally, focusing on the development direction of mutualism, suggestions for the development of paid services in China’s newspaper industry are put forward from the perspectives of technology, audience, and policy.