The invention discloses a multistage electric pump for improving coarse-particle solid-liquid two-phase slurry. The multistage electric pump comprises an electric pump outer shell, a dual-output-shaft submersible motor with a thrust bearing, an upper pump and a lower pump, wherein the dual-output-shaft submersible motor, the upper pump and the lower pump are arranged inside the electric pump outer shell, the upper pump and the lower pump are respectively arranged on an upper-end output shaft and a lower-end output shaft of the submersible motor, a two-channel annular runner is arranged between the electric pump outer shell and an outer shell of the submersible motor, two ends of the two-channel annular runner are in seamless connection with a runner of the upper pump and a runner of the lower pump through an upper suction shell and a lower suction shell so as to form an integral runner of the electric pump, and the coarse-particle slurry can smoothly flow through the runner or flow back. According to the invention, the problem of runner blockage of coarse particles caused by detainment or backflow in the runner is solved, and the multistage electric pump has the characteristics of reasonable structure, simplicity for operation, capability of allowing the large coarse particles to flow through and flow back, high lift and the like.