In order to provide helpful information for maize variety selection and realizing high yield, the grain filling characteristics of 18 summer maize varieties were investigated under 6/10 (S1), 6/20 (S2), and 6/30 (S3). The results showed that: (1) There were significant differences in the final 100-grain dry weight among varieties and sowing date treatments, characterized by S1 (35.20 g) > S2 (33.45 g) > S3 (31.38 g), and the range of variation was 28.50 g (HM 1) to 36.37 g (JNK 728). (2) The average filling rate (Gave) under different sowing date treatments was S1 (0.74 g 100-grain -1d-1) > S2 (0.65 g 100-grain -1d-1) > S3 (0.57 g 100-grain -1d-1). The average grain filling rate of S1 was 0.09 g 100-grain-1d-1and 0.17 g 100-grain-1d-1 higher than that of S2 and S3, increased by 13.85% and 29.82%, respectively. The Gave of JNK 728 (0.75 g 100-grain -1 d-1) was the highest among varieties, which significantly higher than ZD 958 and XY 335 (0.58 g 100-grain-1 d-1 and 0.67 g 100-grain-1 d-1), increased by 29.31% and 11.94%. The active grain filling period (P) showed that S1 (47.85 d) < S2 (51.39 d) < S3 (55.04 d). (3) The yield under different sowing date treatments was S1 (10,628.67 kg hm-2) > S2 (10,207.65 kg hm -2) > S3 (9144.59 kg hm -2), with S1 4.12% and 16.23% higher than S2 and S3, respectively. Among them, NK 815, MC 121, JNK 729, MC 812, JNK 728 and XY 335 had relatively high yields, with an average of 10,730.56 kg hm-2, significantly higher than ZD 958 (10,080.85 kg hm-2), increased by 6.44%. (4) Correlation analysis showed that yield level was significantly and positively correlated with Gave (0.70 **) and grain weight (0.68**), and was significantly and negatively correlated with P (-0.36 **); Grain weight was significantly correlated with Gave (0.58 **). In conclusion, maize yield, grain weight and grain filling rate reduced with the sowing date delay, but P increased accordingly, early sowing properly was beneficial to achieve higher yield in Huang-Huai-Hai summer maize region, by selecting varieties such as JNK 728, JNK 729, MC 812, MC 121, NK 815, and XY 335 which characterized by suitable growing period, higher grain filling rate, suitable active grain filling period and higher yield level. JNK 728, characterized by medium-early maturity, higher grain filling rate and yield, was suitable for the later sowing conditions or areas with insufficient accumulated temperature, and could reach physiological maturity in mid-October when sowing at the end of June.