The invention discloses a synergistic acaricidal composition containing abamectin. According to a preparation method, N-(5-tert-butyl-1,3,4-thiadiazole-2-yl)-N'-(2,6-dichloropyridine-4-yl)-N, 4-dimethyl-1,2,3-thiadiazole-5-formamidine (TDCA-6) and abamectin are taken as the active ingredients, and the synergistic acaricidal composition is composed of the active ingredients and pesticidally acceptable auxiliary ingredients, wherein the weight ratio of TDCA-6 to nicosulfuron is controlled to be 10:1 to 1:60. It is shown by laboratory experiment and field pharmacological experiment that no antagonism is caused by combination of the two active ingredients, obvious synergistic effect is achieved, and the synergistic acaricidal composition is safe to crops.