Research conclusions:(1)The characteristics and mechanical properties of the karst caves ofQipanshi Tunnel are analyzedwith geological knowledge, and the location and size of the caves in the leftside of tunnelwall are speculated.(2)The ground probing radar is used to probe the left side of tunnelwall and the tunnel bottom, and the probing result shows thata large karst cave exists in the left side of the tunnel and it conforms to the speculated results, except the deviation in position. The reasons for the deviation are analyzed. (3)The comprehensive geological knowledge and geophysical equipmentare two necessary conditions to do the geological forecast perfectly.