Ben1 oil reservoir and AG1 oil reservoir of Jake South Oilfield in Fula sag of Muglad Basin are typical complex fault-block oil reservoirs，which are anticline oil reservoir and layered oil reservoir developed in the complex fault block re?spectively. A number of low resistivity pays were ound in Ben1 oil reservoir and AG1 oil reservoir，which added to the difficulty of net pay identification. So the data，such as core data，test data and logging data，were comprehensively used to study the genesis and control factors of low resistivity pays. First，the reservoirs in Ben1 oil reservoir and AG1 oil reservoir were categorized according to their grain size，petrophysical properties，pore type and tightness，and low resistivity pays were defined in each type of reservoir. Then cores，thin sections，petrophysical data，SEM and X-ray diffraction data were comprehensively used to study the genesis of the low resistivity pays. Finally，the relationship between the identified low resistivity pays and the reservoir characteristics was studied to seek the controlling factors of its distribution. The results show that the main genesis of the low resistivity pays were high bound water saturation，low oil saturation caused by insufficient hydrocarbon charging and existence of conductive minerals，while additional conductivity of clay minerals and other engineering causes have little effects. The genesis of low resistivity pays found in different reservoir types and in different complex fault block types were different. The distribution of low resistivity pays was controlled by sedimentary microfacies，reservoir types and low resistivity pay belts，generally by one or two factors. The next exploration and development of the low resistivity oil layer in the study area should be mainly aimed at the high-quality reservoir in Ben1 oil reservoir and AG1 oil reservoir.