The Asian pear moth (Grapholita molesta) is one of the most significant pests affecting pear orchards in China, causing extensive damage to fruit production. Over the past few decades, the widespread use of organophosphate and pyrethroid insecticides to control this pest has led to concerns about the evolution of pesticide resistance. This study investigates G. molesta populations' development of resistance to these two major classes of insecticides commonly used in Chinese pear orchards. We conducted a series of laboratory bioassays to evaluate the susceptibility of G. molesta larvae and adults from multiple orchards in key pear-growing regions of China to a selected organophosphate (chlorpyrifos) and pyrethroid (deltamethrin). The study also examines the underlying mechanisms of resistance, including metabolic detoxification through cytochrome P450 enzymes, esterase activity, and mutations in the target site of the insecticides. Our results show a significant increase in resistance ratios among G. molesta populations to both organophosphates and pyrethroids, with some populations exhibiting resistance levels up to 20-fold higher than susceptible strains. Resistance was most pronounced in regions where chemical control has been heavily relied upon for multiple seasons. Enzyme assays revealed elevated levels of P450-mediated detoxification in resistant populations, and molecular analysis identified key mutations in the voltage-gated sodium channels of pyrethroid-resistant individuals. These findings highlight the adaptive potential of G. molesta to pesticide pressure and underscore the risks of prolonged chemical use without rotation or integrated pest management (IPM) strategies. This study provides a comprehensive understanding of the mechanisms driving resistance in G. molesta and emphasizes the need for sustainable pest management practices in pear orchards. To mitigate further resistance development, we recommend the adoption of IPM approaches that integrate biological control, alternative insecticides with novel modes of action, and resistance monitoring to ensure the long-term viability of chemical control in pear production.