Abstract: High frequency transformer is a kind of electric energy conversion equipment that combines power electronic technology with high frequency magnetic link technology. Compared with power frequency transformers, HFT has the advantages of small size and light weight, so it has a wider range of applications in modern converters. However, there are still many problems to be solved in the application of HFT. On the basis of introducing the development history of HFT, this article summarizes the basic principles and calculation methods of HFT, introduces the parameters such as leakage inductance and distributed capacitance, summarizes the calculation methods of winding and magnetic core losses, and generalizes the optimal design technology of HFT, such as the magnetic core optimization technology, the winding optimization technology, the prototype design and manufacturing technology and the multi-physics simulation. Finally, it summarizes the remaining problems and prospects the development direction of HFT. This article has certain reference value and learning significance for the HFT-related researchers and producers.