A method for estimating a phase error existing in a receiver of a MIMO OFDM communications system is disclosed. The method includes executing Hermitian transpose on channel coefficient matrix of the MIMO OFDM communications system for generating Hermitian-transposed channel coefficient matrix, multiplying received signal matrix of the receiver with the Hermitian-transposed channel coefficient matrix for generating converted signals, summing products of the converted signals and complex conjugates of pilot signals corresponding to the converted signals for generating a sum result, and generating the phase error according to the sum result, the converted signals, and the complex conjugates of the pilot signals. The pilot signals are extracted from the received signal matrix.