Embodiments of this disclosure disclose a method for determining a search space parameter and a terminal device. The method includes: receiving dedicated signaling, where the dedicated signaling is used to configure a TCI state of a CORESET #0 for the terminal device, and a Source RS indicated by the TCI state of the CORESET #0 is a CSI-RS; determining a target SSB having a first association relationship with the CSI-RS; and determining parameter information of a search space #0 in the CORESET #0 based on the target SSB.