Abstract:Irregular-shaped geologic body can be approximated to a 2-D polygon that has optional sides. Then,horizontal and vertical derivatives (particularly the high-order derivatives)of its gravity anomaly can be forward computed by applying difference quotient principle. Theoretical. and real data results show that our method brings quite good accuracy. For example,theoretical forward result of vertical fourth derivative of gravity anomaly resulting from a horizontal circular cylinder was compared with the difference quotient method result that was obtained by approximating 100-side polygon to cross section of the circular cylinder,which only found the error of 0.2%.This method was used to estimate the fourth derivative of gravity anomaly in Gaoyang area. Thus,four local anomalous bodies were displayed,which correspond to four buried hills in seismic section.