Abstract: Susceptibility of nine field populations of Colorado potato beetle Leptinotarsa decemlineata adults from northern Xinjiang Uygur autonomous region to 4 neonicotinoid insecticides,including imidacloprid,acetamiprid,thiamethoxam and thiacloprid,was evaluated by a topical bioassay in 2009 and 2010.The sensitivity of the pest to imidacloprid and thiamethoxam was reduced yearly.Half of the 6 tested field populations developed low levels of resistance to acetamiprid and thiamethoxam in 2009.All the 6 tested field populations exhibited resistance to thiamethoxam in 2010,among them 3 populations showed low level and the other 3 populations showed moderate level of resistance to thiamethoxam.There may be cross-resistance between thiamethoxam and lambda-cyhalothrin in the pest.