The aim is to infer the phylogenetic relationships of Galerucella and outgroup Phaedon brassicae Baly beetle species (Coleoptera: Chrysomelidae) and to discuss the relation between the evolution of Galerucella and host plant. The sequences of mitochondrial cytochrome oxidase subunit Ⅰ (COⅠ) gene were sequenced or downloaded from GenBank for the following species: G. birmanica, G. nymphaeae, G. grisescens, G. suturalis, G. capreae, G. lineola, G. viburni, G. pusilla, G. calmariensis, G. tenella, and outgroup P. brassicae. Nucleotides composition, transition and transversion, and genetic distance of a 720 bp segment were analyzed. By using Maximum Parsimony (MP), Neighbor-Joining (NJ) and Bayesian Inference (BI) methods, we constructed the molecular phylogeny of these species based on their COⅠ sequences. The results indicated that average A+T content of COⅠ gene in Galerucella was 71.8%, showing a strong A+T bias. The variation ratio of amino acid was 18.3%. Genetic distances between Galerucella and the outgroup P. brassicae (0.169-0.198) were bigger than those among Galerucella species (0.001-0.134). Molecular phylogenetic trees obtained suggested that there was remarkable relationship between the evolution of Galerucella and host plant, and G. suturalis, G. capreae and G. viburni have closer relationship with species of Galerucella than as defined in traditional taxonomy.