In order to construct effective and steady plasma source, and to improve the propulsion efficiency of hydronium storm engine, this paper studies the power coupling mechanism of RF wave in the plasma. Based on the steadystate process of the gas with RF heating after being ionized under condition of the plasma density parabolic distribution, the paper studies the power absorbed from RF wave motivated by Nagoya III. The HELIC program is used to solve four coupled radial differential equations for each kz to obtain the energy absorption, wave field and current density along different direction. After analyzing the effect of the radial pressure configuration on the power deposition wave field and current density in the plasma, the result shows that under condition of the positive pressure gradient, the power deposition near the boundary of the plasma weakens, but the penetration depth of the RF wave increases, The distribution of electric field along different direction increases. Different pressure gradient makes the electric field and current density increase remarkably near the boundary of the plasma.