Abstract: The effects of the main climatical factors, including light, air temperature and relative humidity, on the photosynthesis of corn (Zea mays) in a shelterbelt network ecofield in the Song-Nen Plain, Northeast China were studied. The results showed that, during the entire season, the photosynthetic rate of corn was positively correlated with air temperature and light intensity and that the diurnal photosynthetic yield was positively correlated with air temperature and relative humidity. There existed an obvious midday depression as reflected in the diurnal curves of the photosynthetic rate of the corn in the west and east sides near the tree belts in the shelterbelt network. This phenomenon was hardly detectable in the corn growing in the center of the tree belt. Correspondingly, the corn plants growing in the central position showed higher photosynthetic yield than those growing in both sides. Through a synthetic analysis, we found that low air humidity was the primary factor causing the midday depression of photosynthesis of the corn plants in our study site, and air temperature and humidity were the main climatic factors limiting the photosynthesis of corn in the Song-Nen Plain, with air temperature being the most critical one. The shelterbelt network could increase the air temperature and humidity in the belt, thus increasing the photosynthetic yield of corn.