Dynamic epicardial mapping is an important tool in cardiac electrophysiology. This article brings forward a method for 3D dynamic modeling used in epicardial mapping system. Firstly, 3DMAX was used to create a 3D heart model and an .ase file was stored. Secondly, OpenGL was applied to display this model in user's window interface. When electrodes and amplifiers sampled new data, the electrode which had the minimum euler distance to each vertex of 3D model was calculated, thus an interpolate triangle was formed by combining another two adjacent electrodes. The voltage value of each vertex was obtained by using a new linear interpolation based on grads calculation. This method was proved to be feasible in animal experiments. Electrical activity could be investigated directly in a cardiac cycle through this 3D model. This model can also reflect the conduction process of depolarization in complex arrhythmia such as atrial fibrillation. This method is appropriate for any real-time 3D dynamic field modeling, which has an array of regular measure points.