Taking Pinduoduo, a social e-commerce platform, as the research object, an exploratory single case study is carried out. Its disruptive innovation is divided into two stages: entry into the sinking market and erosion of the mainstream market. The path of disruptive innovation through matching and co-evolution of technological innovation and business model innovation is analyzed. Based on the existing research,the triggering mechanism model of disruptive innovation was constructed . The results show that: first, in the process of disruptive innovation, technological innovation and business model innovation are matched and co-performed. They form a spiral chain under the matching and co-performance.Second, disruptive innovation should be realized in stages. Its triggering mechanism includes preconditions, breakthrough and driving factors. At different stages, technological innovation and business model innovation are the preconditions and breakthroughs respectively. The internal and external environment is the driving factor. Third, in the process of disruptive innovation, enterprises must fully consider the driving role of internal and external environment. On the one hand, it is necessary to pay attention to internal technological innovation ability and enterprise strategy. On the other hand, external market competition and market demand also need to be paid attention to.