[Objectives]  To quantify phenotypic variation in the Asian long-horned beetle (ALB), Anoplophora glabripennis (Motschulsky), a widely distributed wood-borer in China, which morphological and molecular research indicates is probably synonymous with A. nobilis (Ganglbauer). [Methods] Phenotypic variation in 13 phenotypic traits in 20 natural ALB populations was studied and analyzed using ANOVA and hierarchical cluster analysis. [Results] There were significant differences in all 13 traits among populations and among individuals within populations. The main source of phenotypic variation was that within populations, the mean coefficient of phenotypic differentiation (V_st) was 11.78 %. Posterior wing length was negatively correlated with longitude, positively correlated with altitude, and negatively correlated with annual precipitation. V_st for elytra color between different geographic populations reached the maximum value of 50.53%. However, classification based on elytra color greatly reduced V_st between two types. [Conclusion] This study was the first to apply digital quantification of elytra color to coleopteran classification, an approach that drastically reduced the apparent coefficient of phenotypic variation between groups. This indicates that phenotypic differences between groups classified on the basis of elytra color are less than those caused by geographical isolation. Pending further validation, ALB and A. nobilis are probably different types of the same species.