Experiments have been conducted to examine the tail erosion phenomenon by transmitting microwave pulses (1.1 μs, and hundreds of kW power level) through a large Plexiglas chamber filled with dry air at 1 to 2 torr pressure. A theoretical model based on two coupled partial differential equations was established to describe the propagation of intense microwave pulse in an air breakdown environment. One is derived from the Poynting theorem and the other is the rate equation of electron density. They are coupled through the density dependence of the plasma dielectric constant in the Poynting equation, and the field dependence of the ionization frequency in the electron rate equation. A computer simulation of the chamber experiment based on the developed model was then performed for comparison. It was shown that all the characteristic features of tail erosion observed in the experiments can be reproduced by the computer simulation. Furthermore, a transformation of the model equations to a local time frame of reference is properly designed so that these equations can be simplified for efficient numerical analysis.