Litang County ,with an average altitude of about 4 000 m,the proposed long deep tunnel in the territory is one of the constraints of the project for the reconstruction of the national highway 318,the existing questionnaire shows there is a layer of confined water .In order to prevent sudden water inflow in the construction period ,the water chemical analy-sis,isotope test,high pressure permeability test and variable confining pressure penetration test are carried out respective -ly .The occurrence of water environment and the permeability of rock mass are found out ,and then sudden water inflow is predicted by the method of rainfall infiltration ,the method of underground runoff modulus method and dynamic method . The results show that the rainfall infiltration and groundwater runoff modulus method are related to catchment area and rainfall,the tunnel water inflow is assumed the infiltration quantity with large deviations ,groundwater dynamics method calculation results are accurate ,combined with spring flow in the engineering area ,the maximum water inflow in tunnel is 11 759.12 m3/d.By construction and excavation ,and the engineering practice is more consistent .%理塘县平均海拔4000 m左右，境内某拟建的长大深埋隧洞为改建的国道318线制约性工程之一，已有调查表明洞身段存在一层承压水，为预防施工期的涌突水灾害，分别进行水化学简分析、同位素测试、高压渗透试验、变围压渗透测试，查明隧洞赋存水环境和岩体渗透性，进而分别采用降雨入渗法、地下径流模数法、动力学方法对隧洞施工涌突水进行预测，结果表明：降雨入渗法、地下径流模数法均与汇水面积及降雨量有关，隧道涌水量为假定的入渗量，偏差较大，地下水动力学法计算结果较为准确，结合工程区出露泉点流量，隧道最大涌水量为11759．12 m3／d，经施工开挖揭露，与工程实际较为吻合。
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