To solve the problem that there can be several partial discharge（PD） sources and the number of sources is unknown in gas insulated switchgear

the paper proposed a method to separate the mixed signals based on the estimate of source number. The zero-space method is used to estimate the source number when there is no sensor noise and eigenvalue-decomposition method is used to estimate the source number when there is sensor noise. Use the FASTICA to separate the blind sources after the source number is estimated. Research the influence of SNR to the results of blind source separation. Correlation coefficients are used to test separating results in order to avoid the presence of blind source separation. The results of the separation indicate that estimate of source number and blind source separation are useful and practical in ultra high frequency（UHF） signals separation.