This paper reviewed the mediating effects of knowledge sharing between social capital(interaction, trust, shared vision) and innovation(radical innovation, incremental innovation) in small businesses. Based on the responses from 337 responses, the results of mediating effect analysis and path analysis showed that interaction and shared vision effect positively on radical innovation and incremental innovation via knowledge sharing or directly, but trust effects positively only on incremental innovation. Social capital and knowledge sharing have more effects on incremental innovation than on radical innovation.