Hong Kong-Zhuhai-Macao bridge island tunnel project needs to meet the investigation standards of Hong Kong, Macau and Chinese Mainland. Thus it’s necessary to set up an engineering geological unit layer to provide the criterion for geotechnical engineering evaluation. Based on the feasibility stage investigation report, preliminary investigation report, detailed investigation and supplement investigation report, and according to the geological origin and times, soil information rocks and physical & mechanical properties, we unify different specifications divide the engineering geological unit layer in keeping with investigation standards to provide a basis for the Pearl river delta estuaries.