Many hosts utilize the ubiquitin system to defend against viral infection. As a key subunit of the ubiquitin system, the role of polyubiquitin in the viral infection of insects is unclear. Here, we identified the full-length cDNA of the polyubiquitin-C (UBC) gene in Laodelphax striatellus, the small brown planthopper (SBPH). LsUBC was expressed in various tissues and was highly expressed in salivary glands, midgut, and reproductive systems. Furthermore, the LsUBC expression profiles in the developmental stages showed that LsUBC was ubiquitously expressed in seven developmental stages and was highest expressed in female adults with SBPH. qRT-PCR analyses indicated that rice stripe virus (RSV) infection promoted the LsUBC expression. Knockdown of LsUBC mRNA via RNA interference increased RSV accumulation. These findings suggest that LsUBC inhibits RSV accumulation in L. striatellus.