Nonlinear dynamic processes with time-varying time-delay can be encountered in industry. The time-delay estimation for the nonlinear dynamic system with time-varying time-delay is an important issue for system identification. In order to estimate the dynamics of the process, a dynamic neural network with external recurrent structure is applied to the modeling procedure. In the case where time-delay is time varying, a useful way is to develop on-line time-delay estimation mechanisms to track the time-delay variation. In this paper, two schemes respectively called direct as well as indirect time-delay estimators are proposed. The indirect time-delay estimator considers the procedure of time-delay estimation as a nonlinear programming problem. The direct time-delay estimation scheme on the other hand applies a neural network to construct a time-delay estimator to track the time-varying time-delay. Finally, two numerical examples are illustrated for the test of the proposed methods.