A beam detection method performed by a network device, the method comprising: • notifying a terminal device of information about a plurality of broadcast beams (step 102); • receiving a detection result about two broadcast beams among the plurality of broadcast beams from the terminal device, the detection result being a detection result of broadcast beam detection performed by the terminal device based on the information about the plurality of broadcast beams (step 104), wherein the detection result comprises: ∘ a detection result of a first broadcast beam whose signal quality is highest, and ∘ a detection result of a second broadcast beam whose signal quality is second highest, the second broadcast beam being spatially adjacent to the first broadcast beam; • determining, based on the detection result, a first downlink beam used for data communication, the first downlink beam being located in one of the first and second broadcast beams, wherein before notifying the terminal device of information about the plurality of broadcast beams, the method further comprises: receiving information that is sent by the terminal device and that is about a second downlink beam used for data communication with the terminal device; and determining based on the information about the second downlink beam, a broadcast beam related to the second downlink beam, wherein the second downlink beam used for data communication with the terminal device is a downlink beam whose signal strength is highest or a downlink beam whose signal quality is higher than a preset threshold, and wherein the broadcast beam related to the second downlink beam used for data communication with the terminal device is at least one of the following: a broadcast beam in which the second downlink beam is located, and a broadcast beam spatially adjacent to the broadcast beam in which the second downlink beam is located. • notifying a terminal device of information about a plurality of broadcast beams (step 102); • receiving a detection result about two broadcast beams among the plurality of broadcast beams from the terminal device, the detection result being a detection result of broadcast beam detection performed by the terminal device based on the information about the plurality of broadcast beams (step 104), wherein the detection result comprises: ∘ a detection result of a first broadcast beam whose signal quality is highest, and ∘ a detection result of a second broadcast beam whose signal quality is second highest, the second broadcast beam being spatially adjacent to the first broadcast beam; ∘ a detection result of a first broadcast beam whose signal quality is highest, and ∘ a detection result of a second broadcast beam whose signal quality is second highest, the second broadcast beam being spatially adjacent to the first broadcast beam; • determining, based on the detection result, a first downlink beam used for data communication, the first downlink beam being located in one of the first and second broadcast beams, receiving information that is sent by the terminal device and that is about a second downlink beam used for data communication with the terminal device; and determining based on the information about the second downlink beam, a broadcast beam related to the second downlink beam, wherein the second downlink beam used for data communication with the terminal device is a downlink beam whose signal strength is highest or a downlink beam whose signal quality is higher than a preset threshold, and wherein the broadcast beam related to the second downlink beam used for data communication with the terminal device is at least one of the following: a broadcast beam in which the second downlink beam is located, and a broadcast beam spatially adjacent to the broadcast beam in which the second downlink beam is located.