A new-type slit spatial filter is proposed, which consists of a pair of cylindrical lens, a filtering slit, and a right-angle mirror.A pair of cylindrical lens and a filtering slit are used to form a one-dimensional filter structure.The right-angle mirror is used to rotate the wavefront 90°and reflect it back to the one-dimensional filter structure for another dimension of spatial filtering, thereby achieving complete filtering of the beam.Based on the Rayleigh-Sommerfeld diffraction integral, the transmission of the beam in the new slit filter was theoretically simulated using Matlab software. Combined with experimental verification, proving the image relay and spatial filtering functions of the new slit filter structure. The new-type slit spatial filter is similar to the folded structure of the three-lens slit spatial filter, so it is nearly half shorter in length, which can further reduce the scale and cost of large laser devices.