[Background] The cotton mealybug, Phenacoccus solenopsis Tinsley, is an important invasive pest, which has spread rapidly and caused serious damage in China in recent years.[Method] During 2009 to 2015, we investigated the infestation of P. solenopsis in Hangzhou. We also identified the plants on which mealybug were present and constructed a phylogeny tree based on mtDNA COI sequencing.[Result] The results showed P. solenopsis were dispersedly distributed in Yuhang, Xiaoshan and Lin'an counties of the Province of Hangzhou. Altogether presence of the mealy bug 68 plant species from 61 genera and belonging to 38 families were recorded, among which Capsicum annuum, Solanum melongena, Solanum lycopersicum, Cucurbita moschata, Gossypium sp., Sesamum indicum, Dendranthema morifolium, Ixeris polycephala, Portulaca grandiflora and Lantana camara caused the most damage. Based on mtDNA COI sequences, the results showed there was no obvious genetic differentiation among the populations of P. solenopsis from Hangzhou. The phylogenetic analysis revealed the P. solenopsis from Hangzhou shared 99.4%~100% identity with others from China.[Conclusion and significance] The results provided the theoretical foundation for the studies of genetic evolution, invasive ways, prevention and control of P. solenopsis.