Teams are one of the most important organizational forms for complex innovation activities, and team science, which focuses on exploring the interaction processes and efficiency enhancement in team innovation, has become a popular research field. The essence of innovation lies in knowledge combination, and introducing new knowledge into teams is a key approach to enhancing team innovation capability. However, how this new knowledge influences innovation performance remains unclear. This paper proposes the concept of team knowledge freshness to define and measure the new knowledge combination from the perspective of team knowledge composition. Based on this, the study investigates the impact of knowledge freshness on innovation performance from three dimensions: innovation quantity, innovation quality, and innovation breadth. The findings are as follows: There is an inverted U-shaped relationship between team knowledge freshness and various dimensions of team innovation performance; When the same amount of new knowledge combination is introduced into a team, the greater the knowledge distance within the combination, the more it contributes to improving team innovation performance; Small teams and large teams exhibit opposite patterns: small teams are better suited to medium-to-low levels of knowledge freshness, while large teams perform better with high levels of knowledge freshness.