The current Venus climate is largely regulated by the global coverage of sulfuric acid clouds. However, the cloud physics with binary condensation of H2SO4 and H2O in the Venus atmosphere has not been fully explored. Previous theoretical studies either assumed a fixed cloud acidity to understand the cloud structure, or assumed that both sulfuric acid and water vapor follow their saturation vapor pressure curves. A self-consistent understanding of the cloud mass loading and cloud acidity is still lacking. In this study, we developed a one-dimensional cloud condensation model coupling condensation, diffusion, sedimentation and simple chemistry of H2SO4 and H2O. Our model is able to successfully explain the observed vertical structure of cloud mass loading, cloud acidity, H2SO4 and H2O gases from Pioneer Venus, Venus Express, Akatsuki and ground-based telescopes. We will present the complicated interaction between the H2SO4 and H2O and that between vapor and clouds. We find that H2SO4 gas can be significantly supersaturated above the middle cloud top when its chemical production rate is large. Our study also implies that the Venus cloud structure might have experienced a long-term variation following the SO2 decadal fluctuations observed by Pioneer Venus and Venus Express. Future Venus missions like DAVINCI+ may be able to test this trend.