The invention provides a horizontal three-shaft vibrating screen which comprises a sieve box assembly, a base and a vibration exciting system, wherein a material inlet and a material outlet are formed in the sieve box assembly; a material receiving box is arranged at the inlet; the vibration exciting system is connected with the sieve box assembly; an elastic support is arranged below the sieve box assembly, and the sieve box assembly is arranged on the base through the elastic support; the sieve box assembly comprises two side walls, a screen assembly and tension assemblies; the tension assemblies are arranged on two sides of the screen assembly, and are connected with the two side walls of the sieve box assembly; the vibration exciting system comprises a transmission mechanism and a three-shaft vibrating screen system; the transmission mechanism is arranged outside the sieve box assembly; the three-shaft vibrating screen system is arranged in the sieve box assembly; and the transmission mechanism is connected with the three-shaft vibrating screen system. By the simultaneous adoption of three groups of vibrators, the horizontal three-shaft vibrating screen is high in treatment capacity and high in screening efficiency; and the labor intensity is reduced, the yield is increased, and the investment cost is reduced.