The invention provides a foundation soil layer contour map drawing method, and belongs to the technical field of geotechnical engineering investigation, and the method comprises the following steps: S1, building a foundation soil contour map drawing drilling database; s2, processing abnormal data of a foundation soil layer; s3, surveying a drill hole data display point; s4, carrying out drilling and thinning; s5, analyzing the distance between the drill holes; and s6, drawing a foundation soil burial depth contour map. The method is concise in step, convenient to use, high in engineering applicability, rapid and convenient in mapping, high in precision and particularly suitable for foundation soil layer development distribution rule research of regional geology and geotechnical engineeringinvestigation projects.