Advances in research on the resistance of insects to insecticides made by entomologists, insecticide toxicologists, plant protection and pest control experts in China over the past 20 years is reviewed. Insecticide resistance, including cross-resistance and the delay, or prevention, of resistance by applying different insecticides with synergistic effects, is briefly introduced. Studies on the mechanisms of insecticide resistance in insects, including target resistance, metabolic resistance, and penetration resistance, especially the role of the genes such as cytochrome P450s, acetylcholinesterase (AChE), glutathione S-transferase (GST), voltage-gated sodium channel (VGSC), P-glycoprotein (P-gp), actylcholine receptor (AChR), epidermal growth factor receptor (EGFR), and γ-aminobutyric acid receptor (GABAR), and their expression products in the development of resistance, are systematically reviewed.