Tungsten helix is a component of transfer wave tube (TWT), its high frequency loss and heat dissipation become serious with power level and working frequency of TWT increasing. To solve the problems, gold thin films were deposited on the surface of helix in our previous. How is the thermal reliability of gold thin films when helix operates at higher temperature? In this paper, the binding force between gold film and substrate was tested by using nanoscratch. The film binding forces of samples pre-plated copper respectively for 5s,10s,15s,20s and then gold-plated for 1.5h before and after heat treatment were analyzed.The results indicate that the films adhesion of samples after heat treatment show no obvious decrease compared with those of as-deposited samples. Especially, the binding force of the sample pre-plated copper for 10s after heat increases . The thermal reliability of gold films is good.