In the crowded city zones, the serried high buildings will affect the discharging dispersion and flow field of nature gas pipelines greatly. A practical developed city was taken as a case in this paper. The cubic geometry model was constructed, and the k-e turbulent diffusion model and SIMPLE arithmetic were adopted to simulate the turbulent diffusion field of urban nature gas pipeline leakage among buildings. The simulations were carried out with three pipeline inner pressure and ambient wind velocities. Based on the simulation results, the fire and explosion hazardous field of leakage gas were analyzed according to its explosion limits. The analysis results indicatod that the turbulent diffusion of CH4 gas was influenced by the pipeline inner pressure, wind velocity and the surrounding buildings. At the same time, the diffusion field was greatly affected by the wind velocity which caused an obvious offset from the vertical axis. This phenomenon will increase the hazardous gas density and the risk level in the side of buildings against the air flow. It is meaningful for the construction of urban flammable pipelines.%在人口密度为三级和四级的城区内,密集的高建筑物对天然气管道泄漏后的扩散和流场形成产生重要影响.本文以某城市的实际情况为例,建立多建筑物的空间几何模型,采用k-ε湍流方程,SIMPLE算法,模拟了在三种不同风流速度、三种不同压力条件下,城区天然气管道泄漏气体在多建筑物地形中的扩散情况.根据模拟结果,依据天然气的爆炸极限,对模拟结果及其火灾爆炸危害的范围进行了对比分析.结果表明,CH4气体的泄漏扩散同时受管道压力、风流速度和周围建筑物的影响；同时受当地风速的影响,泄漏气柱在风流作用下会发生偏折,造成阻挡风流的建筑物内侧危险气体浓度升高,大大增加建筑物周围环境的危险性.研究结果对城区天然气管道的建设具有一定的指导意义.
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