Provided in the present application are a physical downlink control channel detection method and a related apparatus. A terminal device receives indication information sent by a network device side, wherein the indication information may include an association relationship between search space sets, and a specified monitoring mode of the terminal device. The terminal device can determine, on the basis of the indication information, an associated MO which is used for the same PDCCH, such that the terminal device can narrow a blind detection range, thereby effectively reducing the number of times of blind merging of candidate PDCCHs during PDCCH joint detection and decoding. The problem of it being impossible for a terminal device to detect a PDCCH within the scope of a monitoring capability is alleviated, thereby improving the success rate of PDCCH transmission.