The development of a radial-inlet structure cyclone separator is reported in this paper, which is used as a primary device for gas-particle separation in an opposed multi-burner (OMB) gasification system. The radial-inlet cyclone is more suitable for a high-pressure industrial operation environment on the premise of higher efficiency. A model based on computational fluid dynamics (CFD) techniques was applied to study the performance of a new-type cyclone separator In the approach, the turbulent flow was described by the Reynolds stress model, and the particle flow was described by the stochastic Lagrangian model. The validity of the proposed approach is verified by the good agreement between the measured and the predicted results. The results indicate that, though the velocity flow field is not geometry symmetrical and a three-dimensional unsteady state, it is quasi-periodic. Additionally, there exists a processing vortex core phenomenon in the cyclone. The particle concentration distribution is nonuniform because of the centrifugal force The distribution area can be divided into three parts according to the particles' motion feature And the larger particles are easier to separate than the smaller ones. But particles with a size exceeding a critical value will not be collected at the bottom and stagnate on the conical wall of the cyclone. This will lead to serious erosion on the conical part in the cyclone. In addition, the separation efficiency increases with the particle size, and the cut-point diameter of the radial-inlet cyclone is smaller than the traditional cyclone under the same inlet conditions.