III-V group GaN based materials as the third generation of semiconductors have important application prospect in photonics and microelectronics fields. GaN epitaxial film is mainly used for blue-ray or ultraviolet luminescence devices, high temperature electronic devices, detectors, and high-speed field-effect transistors etc. Due to the lattice and heat mismatches between GaN and substrates, the growth of high quality GaN epitaxial film has become one of focused research areas and is always attracted the more attention. Currently, sapphire as substrate has been mostly used for GaN based devices. However, due to its hardness, poor thermal performance, complex processing and expensive price, using GaN epitaxial film for high-power devices is difficult. Si can be used as another substituted substrate because of its high quality, low cost, easy cleavage, good conductivity, and mature Si base integration technology. If choosing silicon as a substrate for GaN epitaxial films, it has to solve the problems of the lattice mismatch by growing a buffer layer. In this paper, several types of buffer layers used for GaN epitaxial films have been introduced. Through analyzing the growth conditions of different buffer layers, how to choose a suitable buffer layer for growing high quality GaN epitaxial films has been proposed.