A mode switching method in a WI-FI network includes after a terminal device accesses a WI-FI network, the terminal device communicates, in a multiple-input multiple-output (MIMO) mode, with an access point that provides an access service of the WI-FI network. The terminal device obtains first received signal strength and a first throughput of the WI-FI network in the MIMO mode, and when the first received signal strength is greater than a first strength threshold and the first throughput is less than a first throughput threshold, the terminal device switches from the MIMO mode to the single-input single-output (SISO) mode.