To solve the problem of signal mixing of interference sources in the research of electromagnetic environmental effects of the equipment, the application of the blind-source-separation algorithm in the signal separation of mixed interference sources is discussed. Usually, the number of source signals should be estimated before using the blind-source-separation algorithm. In this paper, the dimensions of the initialized unmixed matrix are set based on the number of observed signals, and then the signals whose number is the same as that of observed signals can be obtained by separation. Through the correlation detection of the separated signals, the source signals are separated at last. Thus the prior estimation of the number of the source signals can be avoided. The feasibility of the proposed method is proved by the simulation experiment.