The primary cause for failure of gas well integrity is pipe string leakage, which leads to anomalous annular pressure in gas wells and hence threatens safe production of gas wells. The leakage rate of annulus is the core parameter to judge whether the gas well integrity fails. At present, some companies abroad have instrument which can measure the annular leakage rate at ifeld;but there is no reliable domestic method to determine the annular leakage rate. This paper presents two ways to calculate the annular leakage rate:one is the safety valve method, which makes reference to the leakage rate of downhole safety valve; the other is differential method, which establishes the theoretical model for gas to be leaking in the annulus and determines the boundary conditions by the leakage model through small holes on gas lines. Due to the effect of ifeld pressure relief data, the downhole safety valve method is not applicable on site, so the differential method may be used to calculate the annular leakage rate. The differential method was used for example veriifcation in DN2 gas ifeld of Tarim Oilifeld, and the result agreed well with the real situation, showing that this method for annular leakage rate calculation is reliable and is of some reference signiifcance to the ifeld.%气井完整性失效最根本的原因就是管柱发生泄漏，从而导致气井环空异常带压，威胁气井安全生产。环空泄漏速率是判断气井完整性是否失效最核心的参数。目前，有国外石油公司通过设备现场测量环空泄漏速率，国内还未有可靠的方法确定环空泄漏速率。提出了两种环空泄漏速率的计算方法：一是安全阀法，借鉴井下安全阀泄漏速率的判别方法；二是微分法，建立气体在环空泄漏的理论模型，并通过输气管道小孔泄漏模型确定边界条件。由于现场泄压数据的影响，井下安全阀法不适用于现场，可采用微分法进行环空泄漏速率计算。应用微分法对塔里木油田DN2气田进行了实例验证，与现场实际吻合较好，表明该环空泄漏速率计算方法较为可靠，对现场生产有一定参考价值。
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