In recent years, the micro-public welfare model based on social network has been widely used in medical crowdfunding, providing a novel solution for patients facing financial difficulties. Using social networks to eliminate time and space constraints on offline donations, more potential donors can be found. Based on the trust theory, this paper collected the medical crowdfunding projects data of public welfare on Weibo from 2012 to 2018, combined with the number of followers, regions and identity information of the project promoters on Weibo social media, and explored the influencing factors of the amount of public crowdfunding projects by using multi-source data. In the fundraising process of medical crowdfunding projects, the subject of trust construction is the donors, and the object of trust includes not only the relevant information of the patient, but also the promoter and the information characteristics of the project. This paper aims to build a theoretical model of trust from promoters, patients, project information characteristics, so as to explore the factors influencing the fundraising ability of medical projects under the micro-public welfare model. The results show that promoters, patients and project information characteristics can affect the trust of donors, and thus affect the amount of money raised by medical crowdfunding projects. On the basis of the above empirical research, this paper also puts forward some suggestions for the healthy development of micro-public welfare based on the problems found.