Abstract: Because the distribution of underground full-space electric field is disturbed by tunnel vaccum, there are many difficulties in the mathematical simulation and interpretation of DC electric curves in coal mines. Based on model experiments,the regularity of the influence of tunnel vaccum on tunnel roof or floor sounding and on high density geo-electric curves has been discussed in this article.The method of model experiments and tunnel influence coefficient formula（TICF）have been determined.Finally,a case using TICF has been given.