A potential field vector method for quantitative determination of parame-ters of contact plane is described in this paper. Based on the frequency spect-rum expression of potential field, this technique first obtains downward conti-nuation expression of gravity and magnetic anomaly function, and then, with thehelp of the normalized overall gradient nonlinear transformation function, ma-kes quantitative calculation for spatial position, buried depth and dip. In orderto overcome the unstability of the potential field function arising in the courseof its downward continuation towards lower half space, this technique adoptssmoothing factor for displacement of radial frequency with increasing depth.This method enables us to obtain stable calculation results with high preci-sion and to figure out directly spatial parameters of contact plane at depth.These merits have been demonstrated in this paper by means of tentative cal-culations with several models and some examples.