Abstract: The aim of this study was to establish accurate indices to identify and evaluate the deep-sowing tolerance of a range of inbred lines from the maize germplasm. Maize seeds were planted at three depths (3, 15, and 20 cm) and the following phenotypic traits were evaluated: emergence rate (RAT), mesocotyl length (MES), coleoptile length (COL), mesocotyl and coleoptile total length (MES+COL), seedling length (SDL), and root length (RL). At the same time, simple sequence repeat (SSR) markers were used to evaluate the genetic diversity among 51 maize inbred lines. The results showed that as the sowing depth increased from 3 to 15 or 20 cm, the RAT gradually decreased, SDL and RL first increased and then decreased, and MES, COL, and MES+COL increased. There were strong and significant differences in RAT, MES, COL, MES+COL, SDL, and RL among the maize inbred lines. Five traits (RAT, COL, MES, MES+COL, SDL) were significantly affected by sowing depth and by the interaction between genotype and sowing depth. Root length differed significantly depending on sowing depth, but it was not affected by the interaction between genotype and sowing depth. There were strong and significant positive correlations between RAT at 15- and 20-cm sowing depths and MES, COL, MES+COL, SDL, and RL. Six highly deep-sowing tolerant inbred lines and 11 moderately deep-sowing tolerant inbred lines were identified by the membership function method based on their performance when sown at 15 and 20 cm depths. Seventy SSR markers produced 222 alleles with an average of 3.17 alleles per marker. The polymorphism information content for each marker ranged from 0.265 to 0.801 with an average 0.579. The 51 maize inbred lines were divided into two major groups and six sub-groups in a genetic diversity analysis. Relatively high membership values for RAT, MES, COL, MES+COL, SDL, and RL were obtained for the Sipingtou (SPT), Lancaster (Lan), and Luda Red Cob (LRC) lines, which were highly or moderately tolerant to deep sowing. These results showed that maize lines tolerant to deep sowing can be screened by planting seeds at 15 and 20 cm depths, and that RAT, MES, COL, MES+COL, SDL, and RL are important indices to identify deep-sowing tolerance in maize. We conclude that deep-sowing tolerance can be objectively and accurately evaluated by the membership function method in maize inbred lines, and that SPT, Lan, and LRC are important deep-sowing tolerant germplasm groups.