Abstract: This paper adopts nitrogen as background gas, pulsed microwave to produce plasmas, another continuous wave as transmission simulation object, and Global Model with diffusion effect to analyze the evolution of electron temperature and density. The discharge pressure of the experiment is 300 Pa. The results of the experiment display that the reception signals of the continuous wave strongly decay in a short time after the beginning of microwave pulse, but the reception signals of the continuous wave recover slowly when the microwave pulse turns off. The microwave transmission is mainly affected by plasma electron density. The results of Global Model show that electron density increases rapidly, even higher than the critical density of discharge microwave, but decreases slowly when the discharge microwave pulse turns off. This means that the diffusion effect is dominant after plasmas at open space lose the sustained energy, so the electron density will not decrease rapidly and the continuous wave is still reflected, until electron density decreases to the value below the critical density of continuous wave frequency.