Aero-electromagnetic data applied to geological mapping are very important in aero-electromagnetic exploration. These data can not only provide abundant new information of regional geological structure but also improve the exploration effect and raise the recognition capability of anomalies for surveyed objects. At present, the aero-electromagnetic method in China uses three kinds of T-R loop sets. On the basis of their principles, this paper has discussed specialities of the aero-electromagnetic induction secondary field response parameters and their conversion parameters called "mapping interpretation parameters", and pointed out the existing problems in the aero-electromagnetic survey. The mapping technique for lithologic-geological unit was used in Longmen and Wuda areas, with fairly good results obtained.