Sickle seagrass ( Thalassia hemprichii ) is one of the most important marine plants living in the tropical climate, mainly distributed in Southeast Asian waters. It is an important food source for marine herbivores and plays important roles in nitrogen fixation, water purification and maintaining the balance of marine ecology. In recent years, the area of aquatic plants has declined rapidly, affecting the ecological balance. However, the molecular mechanism of aquatic plants has been poorly studied. In this study, all transcriptional information of T. hemprichii was obtained by using high-throughput sequencing technology, and 32,097 unigenes were identified by annotation. In addition, 119 MYB transcription factors genes were screened, and 61 genes with complete ORF were sequenced. Furthermore, 17 clades were identified according to the information of Arabidopsis. This study provides useful information for enriching the genetic information of T. hemprichii, and further exploring the molecular mechanisms of the evolution, development, and physiological functions of Sickle seagrass.