A method to eliminate baseline drift of ECG signal based on improved ensemble empirical mode decomposition is proposed for the disadvantage of poor filtering in traditional method. The method can weaken the mode mixing of empirical mode decomposition, and make up for the shortcomings of EEMD. It establishes the criterion for adding auxiliary white noise in EEMD method, and then determines the two important parameters,i.e., the magnitude of auxiliary white noise and the ensemble times. The method extracts the baseline drift signal from the noisy signal and then reconstructs intrinsic mode function to obtain the "clean" ECG signal, which provides a prerequisite for subsequent research. The experimental results show that the de-noising method, compared with the traditional method, can improve the SNR, reduce root mean square error, keep the characteristic of the waveform, and solve the problem of low frequency component loss.