Abstract: This paper aims to study the effects of maize seed grading on precise sowing quality. Maize seeds were divided into four levels according to the shape and size. Tests on pneumatic and vacuum precise seeder were carried out to investigate the effects on sowing quality such as up to standard reseeding and miss-seeding etc. The experiment results indicated that the pneumatic seeder is more adaptable to the seed size and shape variation. Maize seed grading obviously affects the qualified index and reseeding index, but affects miss-seeding index and coefficient of variation little on condition that all the indexes reach the sowing quality requirements. The qualified index of round seeds was 96%, which was higher than flat seeds with the qualified index was 87.4%. There was great distinction between them. The sowing quality of vacuum seeder was not so good whether the seed graded or not, and has not significant influence on the whole indexes of it. The experiment also shows that pneumatic seeder has better performance than the vacuum seeder.