The invention relates to a radar detection method for the occurrence of a geological structure surface. The technical problem to be solved is to provide a method for enhancing the advanced geological forecast of a ground penetrating radar or the detection correctness and accuracy of a geological radar and avoid large error caused by visual direction or virtual inclination. The technical scheme for solving the problem comprises the following steps of: arranging at least two radar survey lines for a detection target structure surface; testing along the survey lines by using the ground penetrating radar; analyzing and processing data acquired by testing and performing time depth conversion so as to form a radar image; finding out each radar reflected wave event of the same geological structure surface; resolving an equation of the structure surface according to the directions of the survey lines, distance and a reflecting interface depth detected by each residual distance test point; and determining the spatial position of the structure surface according to the true occurrence of the structure surface. The method can be applied to the advanced geological forecast and geological detection of tunnels.