TSSMs were collected from peach (CheongDo area) and apple orchards (ChungJu, KunWi and SoBo areas) in 2005 to investigate LC50s of six kinds of insecticides, fenpropathrin, dicofol, milbemectin, tebufenpyrad, monocrotophos and propargite, against local two spotted spider mite (TSSM) strains, and some selected TSSM strains with insecticides for more than 20 generations were also included in this experiment. Each mite strain was clustered by LC50 value taken from above six selected insecticides treatment. Every insecticide showed about three-fourfold LC50 difference among TSSMs caught in same area. There are no specific differences in LC50 patterns of TSSM to insecticides within peach orchard and among apple orchards. But TSSMs of apple orchard and peach orchard were clustered into different group. Grouping of TSSM strains selected with insecticides in lab artificially showed relationship with action mechanisms of insecticides. The TSSMs selected with monocrotophos and bifenazate, known as acetylcholinesterase inhibitors, and also pyridaben and chlorfenapyr, known as inhibitors of mitochondrial electron transportation, were grouped separately according to action mechanism of insecticide that was treated on TSSM for selection.