The present invention belongs to the technical field of 5G millimeter wave communication and discloses a 5G dual-band up-mixer with switching between amplification function and frequency mixing function, and terminal. The first double-balanced active mixer and the second double-balanced active mixer are connected in series, and both ends of the first double-balanced active mixer are connected with a first transformer and a second transformer respectively; both ends of the second double-balanced active mixer are respectively connected with the second transformer and the third transformer; the first double-balanced active mixer is provided with a first MOSFET and a fourth transformer connected with the first MOSFET; the second double-balanced active mixer is provided with a second MOSFET and a fifth transformer connected with the second MOSFET.