Abstract: To solve drilling problems of slow penetration owing to "slimy" vibration of a PDC bit in the deep and hard formation of Block-12 in Tahe Oilfield,a test of a constant torque converter was carried out in the well section of 1 204.00-4 845.00 m of Well TH121125.Test results showed that torque fluctuation was minor and relatively stable.Compared to offset wells in the same well section,the penetration rate was improved by 20.56%-59.65%,and drilling cycle was shortened by 21.08%-41.39%.In addition,the maximum inclination angle was only 1.07°,and the hole enlargement rate was within 6.42%.Wellbore quality was clearly improved.This indicated that constant torque converter while drilling could effectively eliminate the "slimy" vibration of PDC bit,and protect drill bits and strings so as to make good deviation control and improve drilling speed.