The invention relates to a high-frequency-to-low-frequency adapter. The high-frequency-to-low-frequency adapter includes a low frequency AISG assembly, a high frequency SMA assembly, and a connection assembly, wherein the low frequency AISG assembly includes a housing, a mounting plate on the end part of the housing, a plurality of jacks inserted in the mounting plate, a nut which rotatably sleeves the housing; the peripheral surface of the mounting plate is provided with a clamping bulge; the high frequency SMA assembly includes a dust cap, an SMA housing in the dust cap, an SMA jack inserted in the SMA housing, and an SMA insulator which is arranged between the SMA jack and the SMA housing; the connection assembly is used for connecting the high frequency SMA assembly and the low frequency AISG assembly, and also includes a tail housing which is rotatably arranged between the dust cap and the housing, and a sleeve pipe in the tail housing; and one end of the sleeve pipe is provided with a clamping groove which is coordinated with the clamping bulge. The high-frequency-to-low-frequency adapter can adjust the lettering on the tail housing and the jack position on the mounting plate to maintain the corresponding relation.