Abstract: On account of observation data of a large-fixed loop, a data processing software was designed and developed by C++language in the Microsoft Visual 2008 platform. The conversion of measured data was completed to achieve attenuation curves of the single-channel induced electromotive force and apparent resistivity and sectional drawing of the multi-channel induced electromotive force and the apparent resistivity. That is beneficial to deduce the direction of attenuation of the induced electromotive force and the apparent resistivity of the subsurface geology and to reflect the abnormal position and shape and trend of the geological body. To some extent complement the qualitative interpretation of date of the large-fixed loop.