The Colorado potato beetle (CPB), Leptinotarsa decemlineata Say, is an infamous invasive species worldwide.  It was first found in Xinjiang Uygur Autonomous Region of China in 1993 and spread to Northeast China in 2013.  To better understand the genetic structure and the diffusion path of their populations in China, we used nine polymorphic microsatellite loci to elucidate the genetic diversity, genetic structure and gene flow among nine CPB populations across Xinjiang and Northeast China.  The results show that: (1) Two genetically separated clusters were identified by phylogenetic tree, principal coordinate analysis (PCoA) and Bayesian cluster method.  Cluster one contained populations from Xinjiang, China.  Cluster two contained populations from Northeast China.  A genetic differentiation existed between the two clusters.  (2) Three populations in Northeast China hold an obvious genetic differentiation according to the phylogenetic tree and PCoA, indicating that multiple introductions may occur in Northeast China.  (3) The Altay population in Xinjiang showed a closer genetic relationship with the populations in Northeast China which may be due to the fact that they collectively originated in neighboring Russia.  (4) Among all populations, Mulei and Wusu had obvious gene migrations from Tacheng, indicating that the inland populations are most likely to originate from Tacheng, Xinjiang.