Based on statistical  analysis  of disced rock cores and rockburst about rock mass in exploration adit at the dam site where high ground stressis surrounded the causes of high ground stress are discussed in many respects,  combined with characteristics of ground stress field, including the power source condition which is the regional tectonic setting and geological conditions, power storage conditions which is characteristic of lithology and structure of rock mass, power transformation and adjustment which is late reformation of rock mass. It is considered that high ground stress release is synthetical result caused by factors mentioned above. It provides the powerful reference for the prediction and control of rockburst in the excavation of underground powerhouse.