The invention provides a slurry bed reactor which comprises a reactor cylinder body, wherein a gas leading-in device is arranged at the lower part inside the inner chamber of the reactor cylinder body, a fischer-tropsch wax and catalyst separating device is arranged inside the inner chamber of the reactor cylinder body, a fischer-tropsch wax extracting and back flushing system communicated with the fischer-tropsch wax and catalyst separating device and used for extracting fischer-tropsch wax and back washing to the fischer-tropsch wax and catalyst separating device is arranged at the exterior of the reactor cylinder body; and a gas-liquid separation device positioned above the fischer-tropsch wax and catalyst separating device is further arranged inside the inner chamber of the reactor cylinder body. In the slurry bed reactor provided by the invention, through the arrangement of the gas-liquid separation device, gas flow entering the fischer-tropsch wax and catalyst separating device can be reduced, so that gas is effectively prevented from invading and occupying the surface of a filtration medium, and the effective surface of the filtration medium is improved. Meanwhile, the invention solves the problem of reduced permeability of the filtration medium, which is caused by the fact that catalyst particles are dried up on the filtration medium due to the situation that the gas dries the apertures of the filtration medium.