Based on a rigorous identification of “new quality elements,” this paper constructs an innovative measurement of new quality productivity and empirically examines its common prosperity effect from the perspective of the urban-rural income gap. The results reveal a “U-shaped” nonlinear relationship between new quality productivity and the urban-rural income gap: in the early stages of development, it helps narrow the gap, but beyond a certain threshold, it may exacerbate income inequality. Further mechanism analysis indicates that disparities in labor productivity and human capital between urban and rural areas are the main transmission channels of this effect. Therefore, promoting the development of new quality productivity requires simultaneously bridging the urban-rural “technology divide” to more effectively achieve the goal of common prosperity.