In order to reduce the winding temperature furthest, we adopted the method of adding micron-grade filler to ET-90 base resin, and prepared three kinds of modified high-thermal conductivity adhesive specimens (H-Class). At the same time, four kinds of performance tests (water-absorption, adhesive-strength, breakdown-strength, thermal-conductivity) had been done for them, the test results showed specimen III adhesive had a highest thermal-conductivity (0.31 W/m.K), and finally specimen III adhesive was selected for testing. A new insulating system was developed, it consists of specimen III adhesive, self-made slot wedges and insulating paper. We applied the new insulating system to motors, and observed the changing results of winding temperature and no-load loss. The results showed that the winding temperature could decrease by about 7 K from before, the no-load loss also has a decrease correspondingly. In the meantime, the motor efficiency increases by 0.7% compared to the original state and improves to nearly 86.6%. Thus, this research indicates that this new high thermal-conductivity adhesive (H-Class) could lower temperature in the windings and improve the motor efficiency simultaneously, it is of great significance in practical application.