A new 90° 2×4 hybrid for coherent optical communication systems was designed based on the birefringence effect and the electro-optic effect of crystal. It consists mainly of four pieces LiNbO₃ crystal plates with the same sizes which are modulated by the electric fields and a polarization analyzer. Two of LiNbO₃ crystal plates split respectively incoming signal beam E_S and local oscillator beam E_LO into four beams of laser lights and another LiNbO₃ crystal plates mix them into two synthetic beams by birefringence effects. The desired phase relations between the respective output ports can be obtained by the electro-optic effect. By adjusting the applied voltages on the LiNbO₃ crystal plates, 4 output ports from the polarization analyzer give the mixed beams which are phase shifted by 90° relatively to each other. Compared with traditional optical hybrids, the optical hybrid has the advantage of low losses and good stability of the phase shift.