This application provides a downlink transmitting system and a switching method. The downlink transmitting system includes at least one digital intermediate frequency module group, at least one Tx port group, a plurality of PAs, at least one switching switch, and an antenna array. The plurality of PAs are connected to the antenna array. The plurality of PAs are connected to all Tx ports included in the downlink transmitting system in a one-to-one correspondence. The at least one digital intermediate frequency module group is in a one-to-one correspondence with the at least one Tx port group. Each Tx port group is connected to each digital intermediate frequency module in a corresponding digital intermediate frequency module group through one switching switch. Each Tx port group includes a plurality of Tx ports. A quantity of digital intermediate frequency modules included in each digital intermediate frequency module group is equal to a quantity of Tx ports included in a corresponding Tx port group. Each switching switch includes at least two connection states. Quantities of enabled digital intermediate frequency modules in a digital intermediate frequency module group connected to the switching switch in different connection states are different.