In this paper, When a stable combustion backflow zone is formed in a conventional cyclone, a swirl state will be formed. The excessive airflow will easily blow out the core and limit the efficiency of the combustion chamber . In order to improve the swirl field environment and enhance the combustion stability of the combustor, based on the improvement of the influence of two kinds of axial motion and weak swirl in the precession vortex core, a bi-directional dc pass type with variable cross-section is proposed, and the disturbance of weak swirl can be obviously eliminated by the dc orifice with variable cross-section.Based on the influence of cyclone outlet on air flow, it is proposed that lip outlet makes the center of high-speed air flow empty, thus forming the central low pressure area, which has higher deceleration efficiency and does not form spiral extending air flow.Through the circulation of air - block model design, new types of hydrocyclone in the three main factors affecting the flow resistance model as the foundation, set up seven levels of three factors orthogonal experiment, through the extreme difference analysis and variance analysis, braking slows hole number, hole radius, area of convective resistance than those with significant influence, and get a set of optimum combination parameters .The flow resistance ratio formula derived from the proposed combination is the optimization objective function. When the area of the corresponding reduction plate S is optimized by genetic algorithm, the number of reduction holes n=40 and the radius of the reduction holes R =0.0059m have the best reduction effect, and the total flow resistance ratio is 0.73 after the accumulation of such reduction effects.Through the computational fluid simulation Fluent, the flow rate and pressure at the inlet were used as the simulation conditions. The flow rate and pressure obtained could stabilize the combustion chamber, improve the swirl of airflow, and the lip outlet also formed a low-pressure reflux zone, meeting the design requirements.