[Aim] Monochamus alternatus, has established a symbiotic relationship with, and is the main vector of the pinewood nematode, Bursaphelenchus xylophilus. However, little is known about the symbiotic relationship at the molecular level. microRNAs (miRNAs) are considered to be very important in regulating the growth, development and behavior in animals and plants in post-transcriptional gene regulation.[Method] Eight small RNA libraries were constructed and sequenced by the illumina high-throughput sequencing technology. In addition, differential expression of the identified miRNAs was analyzed, and the function of target genes for these miRNA were predicted by GO annotation and KEGG pathway enrichment analysis.[Result] From these data we identified known miRNAs from the library of beetle's epidermis, fat body, midgut and trachea with nematodes (780+802+617+762), and without nematodes (784+723+713+837). The prediction of target genes function for these miRNAs suggested that miRNAs might participate in metabolism regulation and the immune response of the beetle host.[Conclusion] miRNA plays an important regulatory role in the interaction between M. alternatus and its nematode sybmiont.