Abstract: Abstract：[Objective] The current research aimed to study the relative expression levels of miR-26a and miR-30d in the different tissues, and applying bioinformatic methods to analyze the possible role in cattles.[Method] Total RNA was extractd by TRIzol in the different tissues of Simmental cattle. The relative expression levels of miR-26a and miR-30d were performed by RT-qPCR with specific stem-loop primers based on the mature sequence of bta-miR-26a and bta-miR-30d. The target gene of bta-miR-26a and bta-miR-30d were predicted by TargetScan、RNA22、miRDB.[Conclusion] miRNA-26a and miR-30d all have certain expression level in all kinds of detected tissues, of which miR-26a has the highest expression level in the heart, followed in the spleen, and lowest level in the testis; miR-30d has the highest expression level in the kidney, followed in the heart, and lowest level in the testis. Bioinformatics show that miR-26a and miR-30d may be involved in the regulation of the immune, reproductive activities and so on.