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The topographic effect is one of the essential factors affecting microwave radiation in mountainous regions. This effect&#x0027;s correction can improve the inversion accuracy of key surface parameters. Here, a new terrain correction model in microwave pixel scale is proposed by regression. Using the rugosity (RU) measure the relief of land surface, and analyze its correlation with the brightness temperature difference between the undulating surface and flat surface (<inline-formula><tex-math notation="LaTeX">$\Delta T{B}_{{\varphi }_{Ri}}$</tex-math></inline-formula>). The topographic effects are simulated by the mountain microwave radiation model. Through the regression analysis of the topographic effects with RU in different regions, we find that: first, RU has a linear relationship with the average <inline-formula><tex-math notation="LaTeX">$\Delta T{B}_{{\varphi }_{Ri}}$</tex-math></inline-formula>for different azimuths of the pixel (<inline-formula><tex-math notation="LaTeX">$\overline {\Delta TB} $</tex-math></inline-formula>), with the value of R² above 0.9 for both polarization; then, the effects of azimuths and ground characteristics on brightness temperature can also be corrected by establishing their regression relationship with brightness temperature. Combined with these analyses, an empirical model is developed to measure the topographic effect according to RU. The verification results show that the <inline-formula><tex-math notation="LaTeX">$\Delta T{B}_{\text{model}}$</tex-math></inline-formula> calculated by the empirical model is similar to the <inline-formula><tex-math notation="LaTeX">$\Delta T{B}_{\text{simulated}}$</tex-math></inline-formula> of microwave radiation model (<italic>r</italic> &gt;0.9), which indicates that the empirical model is suitable for mountainous areas with different terrains. Results also provide a theoretical basis for improving the accuracy of passive microwave remote sensing of mountainous areas.