Purpose:Sipunculus nudus is a marine organism with high application value, and the fibrinolytic enzyme (SNFE) extracted from the visceral homogenate has been proved to have an antithrombotic effect by experiments. MicroRNAs(MiRNAs) play an important role in the molecular mechanisms related to plasmin. However, the research on plasmin-related miRNA of Sipunculus nudus is relatively rare. Methods:In this paper, high-throughput sequencing technology was used to sequence and analyze the small RNA and transcriptome of Sipunculus nudus. Conclusion:After data analysis, 198 known miRNAs were identified and 46 new miRNAs were predicted, followed by statistical analysis of miRNA base preference. At the same time, 76 miRNAs differentially expressed in different tissues were found, and a total of 76 known and new miRNAs were predicted for target genes, from which 7,161 candidate target genes were obtained. In addition, we found that six plasmin-related target genes were significantly annotated with 28 GO terms, and three plasmin-related target genes were rich in eight KEGG biological pathways. Finally, four joint regulatory networks including four candidate target genes, 32 differentially expressed miRNA and related proteins were constructed according to the four related species, and it was found that there existed interactions between the candidate target genes Cluster-15745.8440 and Cluster-3821.0 with unclear mechanisms.This study will provide a reference for in-depth exploration of the regulatory relationship between the plasmin-related genes and miRNA in Sipunculus nudus and understanding the molecular mechanisms related to plasmin in Sipunculus nudus. Overall design: High-throughput sequencing technology was used to sequence and analyze the small RNA and transcriptome of Sipunculus nudus