At present， current differential protection is widely applied to electrical equipment main protection. With the wide use of digital protection in power systems， it has been found that current transformer transient saturation can easily result in protection mal-operation. Linear strategy of current transformer anti-saturation for digital differential protection is based on the fact that linear data always exist per cycle during current transformer transient saturation. This specific strategy is to make full use of linear data to prevent ratio restraint differential protection from mal-operating during external faults. Exactly operating current phasor is calculated by half-cycle Fourier algorithm and the only minimum one is selected while restraining current phasor is calculated by full-cycle Fourier algorithm. Dynamic simulation data indicate that the strategy will eliminate the mal-operation caused by current transformer transient saturation during external faults. Finally the prospective application of transformer， generator-transformer and busbar differential protection with linear strategy of current transformer anti-saturation principle is described.