Abstract: In order to increase the slim hole drilling speed at ultra-deep wells in Tahe Oilfield ultra-deep, the reduction turbodrill 127 which has metal surface sealed structure is designed and successfully trial-produced. It has been tested through composite drilling in TH12509 slim-hole well. As a result the average drilling speed of the tested hole section increases more than 80% as compared to that of the same well in adjacent strata and more than 55% comparing with that of the adjacent well in the same strata in condition of turntable drilling. It is indicated that the structure of reduction turbodrill TDR1-127 is reasonable, which has long service life and meets the reqirements of slim-hole composite drilling at ultra-deep wells in Tahe Oilfield.