A switching method and system for a Multiple Input Multiple Output (MIMO) mode are provided by the disclosure. The method comprises that: a NodeB determines to perform MIMO mode switching for a cell (S302); through a NodeB Application Part (NBAP) layer of an lub port, the NodeB sends a message which carries the cell identifier of the cell and the MIMO mode status information of the cell (S304) to a Radio Network Controller (RNC); the RNC updates the MIMO mode status of the cell by using the cell identifier and the MIMO mode status information (S306). The disclosure ensures normal communication between a piece of User Equipment (UE) and a NodeB.