A free-space 2×4 90° optical hybrid with electro-optic modulation is designed and fabricated based on the birefringence effect and electro-optic effect of LiNbO3 crystal. It splits and recombines a signal beam and a local oscillator beam by birefringence effect, and the desired phase shift is introduced by electro-optic effect. It realizes the appropriate function of a 2×4 90° optical hybrid under given electric-field conditions. The performance of 2×4 90° optical hybrid is measured experimentally and analyzed. Experimental results show that the optical hybrid has good performance of phase modulation and the proposed 90°optical hybrid. Its phase shift output is tuned electrooptically and phase errors can be compensated by adjusting the applied electric field. It has potential applications in coherent receivers.