In this paper, we propose a method of stable frequency transfer over a 400~km link without external power supply by combining distributed Raman amplification (DRA) and remote optical pump amplification (ROPA). We elaborate on the advantages of these technologies and their physical limitations in unrepeatered frequency transfer. In this study, by integrating a specially designed ROPA and first-order DRA in a single-fiber bidirectional configuration over a 400~km ultralong-haul unrepeatered frequency link (with an average loss of 0.2 dB/km), a frequency instability of $8 \times 10^{-14}$ at 1~second integration time and $2 \times 10^{-16}$ at 10000 seconds integration time has been achieved.