Abstract: A new pattern for passive location which based on local gravity field model is presented.A fast Fourier series based local gravity field model is firstly introduced，then by which the measured gravity is expressed as continual analytical equation.Finally the classical extended Kalman filter is introduced to estimate the target position with measured gravity as measurement containing the information of target positon.Simulation is done on 0.2′×0.2′ gravity anomaly database，the result shows that the mean error of analytic equation of local gravity anomalies is less than 0.133 1 mGal，and the mean location errors in longitude and latitude are less than 0.777 0 nmile and 1.244 4 nmile respectively.