An electric field model based on baseline and core points is proposed to estimate fingerprint orientation field. Orientation field firstly emerged in baseline and core area. Orientation field near baseline is parallel to baseline which is caused by baseline. Orientation field near core point is changeable which is influenced by core point. Then fingerprint orientation field outspreads. At last, orientation field converges at delta point. This model can explain well why core and delta points exist in pairs in fingerprint images. Experimental results in NIST-4 show that our model can estimate fingerprint orientation field fairly accurately.