Abstract: Taking cold-resistant maize variety Fengdan 3 and cold-sensitive maize variety Zhengdan 958 as test materials, field experiments were conducted in Ⅰ, Ⅱ, and Ⅲ accumulated temperature zones in Heilongjiang Province of Northeast China to study the effects of different accumulated temperature on the photosynthetic performances of different types of cold-resistant spring maize varieties during their grain-filling period. In the three accumulated temperature zones, the tasseling and maturing periods of Fengdan 3 and Zhengdan 958 were prolonged in the order of Ⅰ > Ⅱ > and Ⅲ, and the grain bulk density decreased in the same order. The RuBPCase and PEPCase activities of Fengda
n 3 and Zhengdan 958 leaves had different temperature sensitivity. For Fengdan 3, its leaf RuBPCase and PEPCase activities were high in early grain filling period (0-20 days after anthesis), and the variety could ripen in temperature-limited region. For Zhengdan 958, its leaf RuBPCase and PEPCase activities were high within 0-10 days and 40-60 days after anthesis but not sensitive to the active accumulated temperature during 10-40 days after anthesis, and the variety could not ripen in temperature-limited region. The photosynthetic rates of the two varieties were significantly positively correlated with the active accumulated temperature during 0-10 days and 30-40 days after anthesis. The effects of the accumulated temperature in the three zones on the photosynthetic performances were significant at both early and later grain filling stages. For the same varieties, the higher the active accumulated temperature in grain filling period, the higher the grain yield. Zhengdan 958 had higher yield than Fengdan 3.