Abstract: Black soil is an extremely precious natural resource that plays an important role in ensuring food security, promoting green agricultural development and rural revitalization. However, in the case of overutilization, the quality of black soil deteriorates. Improvement of the adoption rate of conservation tillage by farmers and the growth of the black soil layer from “thin” to “fat” is an urgent issue that needs to be addressed. Previous studies have focused on the impact of economic and policy factors on farmers’ adoption of conservation tillage in black soil areas and pay less attention to the role of social capital embedded in rural areas. Based on the theory of embedded social structure and survey data of 625 farmers in typical black soil areas of Jilin and Heilongjiang Provinces, this study analyzed the transmission path and group differences of social capital and technology cognition on farmers’ adoption behavior of conservation tillage in black soil areas by using a structural equation model (SEM). The results showed that 1) social capital had a positive effect on farmers’ adoption of conservation tillage, in which social networks, social trust, and social norms promoted farmers’ adoption of conservation tillage. 2) Technology cognition played a positive role in promoting farmers’ adoption of conservation tillage. Technology cognition played an intermediary role in the impact of social capital on farmers’ adoption of conservation tillage. The indirect impact of technology usefulness cognition was greater than that of technology usability awareness because farmers more concerned about whether the technology can bring benefits to themselves than whether the technology is easy to master. 3) Multi-group SEM results showed differences in the influence of planting scale and age on farmers’ adoption behavior of conservation tillage technology in terms of social capital and technology cognition. The technology adoption behavior of large-scale growers was more easily affected by social networks, whereas small- and medium-sized farmers were more affected by social trust. Young and middle-aged adults were more likely to be affected by social networks, whereas older adults were more likely to be affected by technology usability. In view of this, in addition to relying on the government, the promotion of conservation tillage technology in northeast black soil areas should give full play to the role of social capital considering the heterogeneity of farmers.