Gallium nitride (GaN) has great potential applications in the field of high-frequency and high-power electronic devices because of its excellent material properties such as wide band gap, high electron mobility, high breakdown field strength. However, the high power GaN electronic device also exhibits significant self-heating effects in operation, such as a large amount of Joule heat localized in the thermal channel, and heat dissipation has become a bottleneck in its applications. The interface thermal conductance (ITC) between GaN and its substrate is the key to determining the thermal dissipation. In this work the various GaN interface defects and their effects on ITC are first discussed, and then some methods of studying interface thermal transport are introduced, including theoretical analysis and experimental measurements. Then, some GaN ITC optimization strategies developed in recent years are introduced through comparing the specific cases. In addition to the common chemical bond interface, the weak coupling interface by van der Waals bond is also discussed. Finally, a summary for this review is presented. We hope that this review can provide valuable reference for actually designing GaN devices.