Research conclusions: (1)Based on the data of geophysical exploration，the anomaly of the lower resistivity can be sorted according to the anomaly shape and the value and the gradient of resistivity．(2)The V，IV andⅢanomaly gradations should correspond respectively with the V，IV and III surrounding rocks．On the other hand，the data of the tunnel excavation demonstrate that only with the data of the geophysical exploration it is difficult to distinguish V surrounding rock and IV surrounding rock．(3)Due to special engineering geological character of basalt，the comprehensive geological exploration，especially the geophysical exploration must be conducted in order to objectively evaluate the general engineering geological condition for the tunnel and rightly instruct tunnel construction．