Ecol-physiological characters including population density and height,leaf length and width,culm lenth,internode length and chlorophyll content of Calamagrostis angustifolia were studied using field survey and controlled experiment for two water regimes.

Considering the complicated situations such as uncertainly in strata pressure, high abnormal pressure coefficient, strata being easy to collapse, co-existence of well blowout and lost circulation etc, the article analyzes technical difficulties of drilling fluid with super high density, decides prescription of drilling fluid with density of over 2.