The ballistic range uses a two-stage light gas gun to launch the model into a hypersonic state, and the model form a plasma wake when flying at hypersonic speed in the target chamber. In order to obtain the radial two-dimensional distribution of transient plasma electron density in the wake of hypervelocity model, a seven channels Ka-band microwave interferometer measuring system was developed. In the transceiver system, one transmitting antenna to achieve plane wave irradiation plasma, and a seven-port array antenna is used to receive plane waves which passing through the plasma, the antenna beam can completely cover the radial range of the wake. Measuring system shortest response time and electron density measurement range of the interferometer measuring system are 1ms and 10¹¹-10¹³/cm³ respectively. Plasma is often treated as layered medium in data processing of multichannel microwave interferometer, consider the effect of refraction on the stratified interface, in this work, the ray tracing(RT) method is used to establish the electromagnetic propagation model, combined with the measurement data to construct the objective function, and the genetic algorithm(GA) is used to invert the radial two-dimensional distribution of the electron density under different test conditions. The result shows that it is in good agreement with the numerical simulation under the same test state, which proves the reliability of the validity of the data processing method. Then, the influence of the layered model on the calculation result is analyzed, which shows that the seven-layers model is suitable for the wake modeling under given experimental conditions, maximizing the number of receiving channels and ensuring the accuracy. RT method is used for the first time to achieve the two-dimensional distribution of electron density in the wake of hypervelocity projectile, and some rules of two-dimensional electron density distribution of the hypersonic model under given experimental conditions are realized.