An epitaxial structure of a GaN-based radio frequency device based on a Si substrate, wherein the epitaxial structure of the GaN-based radio frequency device is composed of a Si substrate, an AlN nucleation layer, an AlGaN buffer layer, a GaN:Fe/GaN high-resistance layer, a GaN superlattice layer, a GaN channel layer, an AlGaN barrier layer and a GaN cap layer which are stacked in turn from bottom to top;
- wherein the GaN:Fe/GaN high-resistance layer is composed of an intentional Fe-doped GaN layer and an unintentional doped GaN layer which are alternately connected;
- each of the intentional Fe-doped GaN layer and the unintentional doped GaN layer has a thickness of 100 nm to 200 nm;
- the GaN superlattice layer is composed of a low-pressure/low V/III ratio GaN layer and a high-pressure/high V/III ratio GaN layer which are periodically and alternately connected, and each of the low-pressure/low V/III ratio GaN layer and the high-pressure/high V/III ratio GaN layer has a thickness of 20 nm to 50 nm.