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In order to address the effects of different seedbed treatment on the morphological characteristics and population uniformity of maize seedlings under no-tillage seeding manners, a field positioning experiment was conducted in June 2018 at the Wanbei Comprehensive Experimental Station in Suzhou, Anhui Province. Four different no-tillage seeding manners were investigated after wheat straw returning to field, including stripe rotary tillage (ST-X), straw mulching tillage (SMT-Y), stripe vertical tillage (ST-Z) and stripe subsoiling tillage (SST). The seedbed soil flatness, transverse maximum height difference, seedling morphological characteristics (leaf age, plant height, stem diameter and root length per plant) and population’s uniformity were determined. Experiment results showed that the average soil flatness of ST-X, SMT-Y and ST-Z was decreased by 7.67mm, 16.33mm and 11.00mm as compared with that of SST of strip subsoiling, respectively, however, only SMT-Y showed significant effect;the seedbed surface flatness from high to low was SMT-Y, ST-Z, ST-X and SST. In addition, the population’s uniformity of maize seedling stage of ST-X, SMT-Y and ST-Z was significantly increased by 4.34, 1.10 and 10.18 percentage points, respectively. The better the surface flatness effect of the seedbed was, the better the population’s uniformity, the worse the soil flatness effect, and the more serious the size of seedlings were. The population’s uniformity from large to small was SMT-Y, ST-Z, ST-X and SST. Due to the large amount of straw covered by the side-slumped (SMT-Y) seedbed, it was difficult to break through the straw layer after germination of maize seeds. Thus the average plant height, the stem diameter and the root length of seedlings were the lowest. Correlation analysis showed that there was a linear and significant negative correlation between soil flatness (SMN), horizontal maximum height difference (Δh) and population’s uniformity of the seedling stage (Q), the correlation coefficients were 0.963 and 0.914, respectively. In summary, the surface flatness effect of the seedbed helped to improve the population’s uniformity of maize seedling stage, the stripe vertical tillage antiblocking manner was preferred among the four no-tillage seeding manners, which could effectively improve the soil structure of plough layer, provide a clean and flat seedbed, inhibit the waterlogging catastrophe of the gully to promote the growth of seedling, therefore this was the most suitable seedbed straw treatment for summer maize no-tillage seeding in Shajiang black soil region of Huaibei Plain.