Abstract: In this paper, Directly Iterative Finite Element Algorithm was used to calculate the electromagnetic components induced by line source on the 2D geo-electric model in frequency domain, and then a convenient and effective digital filter was introduced in the transformation from frequency-domain to time-domain, thus the forward modeling of transient electromagnetic field was achieved. The method features good conveniency of coding, small occupation of storage in computer, faster operation, and simple input of initial model. Comparing with the theoretical results the method showed a good accuracy. This forward method is significant for the study of TEM, and important for 2DTEM inversion.