煤层段水力造穴能够增大煤层透气性，提高瓦斯抽采效率，然而水力造穴钻头的节流控制机理分析计算方法仍不完善。首先，介绍了水力造穴装置的组成、水力造穴的详细过程、水力造穴钻头的结构和原理、节流管的作用机理；将节流管内部流畅简化为一维流体进行分析，根据流体连续性方程、动量方程、伯努利方程3个方程，推导了节流管内部压力分布的数学表达式，绘制了节流管内部压力的分布曲线。其次，依据$ k - varepsilon $湍流模型建立节流管的仿真模型，分析了节流管内部压力分布、流速分布。最后，开展了水力造穴钻头开启关闭试验，研究了水力造穴钻头开启关闭流量和压力的变化、不同节流管缩径直径和压降值之间的关系；为低透煤层瓦斯抽采增透提供钻具支撑，为水力造穴钻头的节流管设计提供借鉴。

Hydraulic cavitation in coal seam can increase the permeability of coal seam and improve the efficiency of gas extraction. However, the analysis and calculation method of throttling control mechanism of hydraulic cavitation bit is still not perfect. In this paper, firstly, the composition of hydraulic cavitation device, the detailed process of hydraulic cavitation, the structure and principle of hydraulic cavitation bit and the mechanism of throttling tube are introduced. Then, the flow inside the throttling tube is simplified into one-dimensional fluid for analysis. According to the continuity equation, momentum equation and Bernoulli equation, the mathematical expression of the pressure distribution inside the throttling tube is deduced, and the pressure distribution curve inside the throttling tube is drawn. Secondly, the simulation model of the throttling tube is established according to the turbulence model, and the pressure distribution and velocity distribution inside the throttling tube are analyzed. Finally, the opening and closing experiment of the hydraulic cavitation bit is carried out, and the relationship between the opening and closing flow and pressure of the hydraulic cavitation bit, the reduction diameter of different throttling tubes and the pressure drop value is studied. This study provides the drilling tool support for gas extraction and permeability enhancement in low-permeability coal seam, and provides the theoretical support for the design of throttling pipe of hydraulic cavitation drill.