Abstract: The fissured rock seepage flow field of Xinanjiang river right dam is studied by using the isotope tracer method.Such hydraulic parameters as flow velocity,flow direction and vertical flow can be obtained with the isotope tracer technique in single boreholes.The coefficients reflecting the permeable characteristics of fissure such as seepage coefficient,equivalent mechanic fissure width etc.are obtained combining with related seepage theories.The distribution of seepage field and the location of concentrated seepage passage are determined by analyzing these coefficients.