A method and device for performing Multi-Input Multi-Output transmission to a mobile terminal in the base station devices of a wireless communication system is provided. Each base station device determines the sector coordination group used at a certain frequency band according to system settings. Each base station device only performs multiple-sector (-cell) collaborative MIMO transmission in the sector coordination group which includes the sectors governed by the base station device. A simple and effective method is provided for realizing the multiple-sector (-cell) MIMO technology, its advantages including but not limited to there being a reduced amount of information exchanged between sectors (cells), which facilitates implementation and management, and good performance in controlling interface between sectors (cells).