Abstract: Three cultivars of maize (the early maturity cultivar of “Luyuandan14”, the medium maturity cultivar of “Yedan22” and the late maturity cultivar of “Yedan13”) were selected to study the effect of maize cultivars on the photosynthetic characteristics and yield of summer maize intercropped with spring maize and monocropped one. The results show that late maturity spring maize cultivar reduces leaf area, light interception rate, chlorophyll content, nitrate reductase activity, and the rate of photosynthesis of summer maize after anthesis under intercropping. To further analyze the relationship between photosynthetic characteristics and the yield of summer maize, the concept of “photosynthetic productivity product (PPP)” was developed. PPP is the product of two or more factors including photosynthetic leaf area, photosynthetic capacity and photosynthetic duration. Compared with single photosynthetic character, PPP is more significantly correlated with yield. Furthermore, the arithmetic product of leaf area, ear leaf chlorophyll content and days after anthesis, and that of leaf area, photosynthetic rate of ear leaf and days after anthesis are more closely related to yield than the arithmetic product of leaf area and days after anthesis. In conclusion therefore, the differences in yield under different cropping systems are the common actions of photosynthetic leaf area, capacity and duration. Thus medium maturity cultivars of spring maize and late maturity cultivars of summer maize are beneficial to total yield under intercropping. PPP provides a new and efficient analytical dimension for yield and quality superiority in intercropping.