Demographic bioassays were carried out in the laboratory to assess the demographic responses with gained resistance of Tetranychus urticae Koch to Vertimec, Cypermethrin, Methomyl and Malathion at two sublethal concentrations(LC50 and LC25) through 40 generations. Life table data were used in each sublethal treatment of parents , F2, F6 ,F10 , F20 , F30 and F40. Life cycle durations ranged from 30.73 to 16.05 days at LC50 and from 23.84 to 11.87 days at LC25 of tested pesticides,resp. Life span durations ranged from 21.71 % to -28.12 % at LC50 and from 17.84% to -30.96 % at LC25 of tested pesticides,comparing with the check. Intrinsic rate of increase (Rm) and two population growth rates(fecundity λ and vitality λ)for T.urticae (hereafter given in units λ /day)were estimated and discussed