A mathematical model is developed to describe the residence lime distribution (RTD) characteristics of the liquid-phase loop reactor, taking into account the capacitance of the recycling pump. Based on the transfer function of the reactor model, the dynamic behavior of the limiting cases is investigated in order to characterize the main modes of macromixing in the reactor vessel. The full mathematical model is then used to simulate the RTD of the loop reactor. The full model comprises a set of coupled parabolic partial and ordinary differential equations and is solved numerically. The numerical approach allows the implementation of a time domain-based parameter estimation procedure for evaluation of the RTD parameters of the reactor model. Tracer pulse experiments are then carried out in a lab-scale polymerization loop reactor in order to provide data for the parameter estimation procedure. II is shown that simulated reactor responses match quite well with experimental data. Besides, the estimation procedure employed is able to provide parameter estimates with high accuracy and low standard deviations. Therefore, the modeling approach presented here may be used for reliable estimation of the macromixing parameters and proper description of the RTD dynamics of loop reactors.