Objectives We explored the physiological differences and molecular mechanism of sorghum under salt stress by excavating the key regulatory genes of sorghum under salt stress and screening and understanding the mechanisms of salt-tolerant and salt-sensitive sorghum materials.

Methods The salt-tolerant genotype "67B" and salt-sensitive genotype "3560R" sorghums were the researched objects. Plants were treated with 150 mmol/L NaCl, while growth index, leaf growth indexes, transcriptome sequencing, and bioinformatics analysis were measured.

Result The results showed that the growth rate of salt-tolerant sorghum was faster, and there was a significant increase in salt resistance. Salt resistance can improve the selective absorption, accumulation and distribution of Na⁺ in plants. Salt tolerant materials can maintain high catalase activity under salt stress, increase range of activity after salt stress, maintain a strong scavenging ability, and remove excess accumulated reactive oxygen species in time. There were 5040 differentially expressed genes in the two strains under salt stress, indicating that the response pathways of salt-sensitive and salt-tolerant materials to salt stress were similar. The distribution of differentially expressed genes of the two materials in KEGG pathways varied greatly. Of the top five gene entries in the two materials, three are the same and distributed in phenylpylene synthesis, plant hormone signals and carbon metabolism, and the other two in salt-sensitive materials are distributed in starch and sucrose metabolism and amino acid biosynthesis, which are related to basal metabolism. The differential genes in salt-sensitive materials mainly focus on basic metabolism and secondary substance synthesis pathway.

Conclusions Salt tolerance mechanism in sorghum is a complex process, which is the result of a series of gene expressions in different pathways, and depends on the balanced expression of multiple genes in a complex network.