The susceptibility of Frankliniella occidentalis（Pergande）to 13 insecticides was evaluated in two Beijing districts, Haidian and Changping, in 2009 and 2010 using a modified TIBS method.The most toxic insecticides were spinosad and emamectin benzoate.The next most toxic were the pyrethroid insecticide cyhalothrin and the phenyl-pyrazole insecticide fipronil.Methomyl and omethoate were the least toxic.In 2009, western flower thrips populations in Haidian and Changping districts were relatively sensitive to the most of the insecticides tested (resistance ratio <3).The Haidian population had decreased susceptibility to chlorfenapyr and deltamethrin (resistance ratios of 4.6 and 4.13).The Changping population had decreased susceptibility to chlorfenapyr, deltamethrin and emamectin benzoate (resistance ratios of 4.61, 4.13 and 3.30 respectively).By 2010, the Haidian population had developed moderate levels of resistance to cyhalothrin (resistance ratio of 39.67), and had decreased susceptibility to deltamethrin (resistance ratio of 4.55), but was still sensitive to the other insecticides (resistance ratios <3).By 2010 the population of Changping developed low levels of resistance to indoxacarb, deltamethrin, methomyl and imidacloprid (resistance ratios of 6.50, 5.79, 5.46 and 9.55 respectively).It also had decreased susceptibility to emamectin benzoate and cypermethrin (resistance ratio of 4.55), but was still sensitive to esfenvalerate and chlorfenapyr (resistance ratio <3).