This application provides a data dimension reduction method, apparatus, and system, a computer device, and a storage medium, and relates to the communications field. The method includes: receiving an antenna domain received signal (201), where the antenna domain received signal includes an uplink signal that is sent by user equipment UE and that is received by an array antenna corresponding to an RRS, the antenna domain received signal is a time domain signal, a dimension of the antenna domain received signal is N 1 , and N 1 is an integer greater than 1; obtaining a received beam weight, where the received beam weight is determined based on channel information of the UE, and different received beam weights are determined based on different channel information (202); and performing dimension reduction on the antenna domain received signal by using the received beam weight, to obtain a beam domain received signal (203), where the beam domain received signal is a frequency domain signal, a dimension of the beam domain received signal is N 2 , and 0 2 1 . A problem of relatively low flexibility of data dimension reduction in a related technology is resolved according to the method.