Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), is the most devastating insect pest that attacks potato crops in fields or storage. Pesticides are important to reduce population of this pest. The intent of this study was to investigate the sensitivity levels of P. operculella population field comparing with a reference to susceptible strain and biochemical analysis of technique(s) engaged in indoxacarb, sulfoxaflor and emamectin benzoate metabolism to 3 different detoxification enzymes (CPR-DPPH, GST-CDNB, and EST- PNPA). Resistance ratios were 11.9, 1.3 and 3.3 folds for indoxacarb, sulfoxaflor and emamectin benzoate, respectively in P. operculella field population. Biochemical analysis displayed that CYP450-DPPH and GST-CDNB activities show no a considerable (p<0.05) superfast compared with susceptible strain, furthermore, EST- PNPA activity showed a 2.7 fold increase compared to susceptible population. Bioassay analyses displayed moderate resistance to indoxacarb while a little resistance showed in at field population to emamectin benzoa of P. operculella. Esterases have a major role in the increase of resistance to indoxacarb, cytochrome P450 may have an elementary role in resistance against emamectin benzoate, GSTs do not apparently involve in the development of resistance against indoxacarb and emamectin benzoate of P. operculella. These results involved important practical application in managing pesticide resistance in P. operculella populations.