Based on the situation perspective, the research, by constructing a collective individual rumor situation interpretation framework and using the Social Network Analysis method, selected 571 online rumors within a diffusion cycle of the COVID-19 pandemic rumors to verify and supplement the downward snowball effect of sociology. The study found that in the rumor diffusion cycle including the outbreak period, the reversal period and the stable period, the rumormongers collectively defined six social scenarios of the COVID-19 epidemic. According to the research, the snowball effect of the rumors ending in the reversal period is the rational communication of mutual structure carried out by the rumormongers to reach a certain potential social consensus and presents a double rolling feature. Finally, the social situation constructed collectively by the hearers has the authority to continuously challenge and dispel official discourse in the middle dimension. Due to data limitations, the research failed to provide explanations in a wider scope, but it is necessary to remain sensitive to the “situation” in the rumors.