Using electromagnetic wave interborehole tomographic imaging(CT)technique,one can find out the distribution of fissures,closely spaced fissure zones and strong medium weathering zones in bedrock of nuclear reactor,study the variation characteristics of electromagnetic wave adsorption coefficients of some fissures or closely spaced fissure zones along profiles in different specific directions within the same borehole,and infer the preferred direction of the distribution of bedrock fissure zones.