This paper outlines the technology and benefits of the downhole electric motor drilling system.This step change in drilling engineering is achieved through drilling motor powered by electricity and downhole signals transmitted by electric cable.The down-hole electric motor drilling system can optimize drilling parameters and increasing drilling speed by controlling WOB,pump displacement and RPM independently & respective-ly.High data transmission can realize ground and downhole communication in real time,providing platform for intelligent drilling.The downhole electric motor drilling system mainly consists of electric drilling motor module,downhole measure & control module,downhole power & signal transmission module and power supply& control module.Apply high power density permanent magnet motor to drive the bit directly.Wet connector and power line carrier etc.,technology real-ize downhole power & signal collinear coupling transmission and electrical bent sub realize downhole azimuth &deviation adjustment in real time.Control of permanent magnet motor with unbalanced three-phase power supply and anti-interference of downhole power & signal collinear coupling transmission etc.,key technology challenge have realized breakthrough by laboratory test of prototype system.The closed-loop vector control technology realize permanent magnet motor work smoothly,power line carrier communication delay decreased from 100ms to 3ms.The success of laboratory test of prototype system might accelerate commercial appli-cation of downhole electric motor drilling system,provide a revolutionary drilling method for oil& gas exploration.