The complex electromagnetic environment in substation may disturb the electrical test in substation. By analyzing the interference signal, the basic principle of the adaptive filter is discussed. An adaptive signal separator are designed according to the minimum mean square error criterion and Least Mean Square (LMS) algorithm. The adaptive signal separator is used to analyze the suppression of low frequency narrow-band interference. With the help of the Fast Fourier Transformation (FFT) algorithm, frequency domain analysis is carried out. Moreover, the suppression of low frequency narrow-band interference is implemented and the practical electromagnetic clean space production device for substation is developed. The feasibility of the proposed design and the efficiency of the device are validated by the simulations in the lab. The field test results in 220 kV and above substations show that the electromagnetic clean space production device for substation based on this method can suppress the interference signal reliably and improve the test efficiency effectively.