Linear modes were investigated in the plasma environment of the Venusian ionosphere under model approximation. Utilizing data from the Venus Express (VEX) spacecraft, we estimate the physical parameters within the ionosphere at altitudes ranging from 400 to 1000 km. A fluid model is employed, consisting of a collisionless, unmagnetized, homogeneous, isothermal fluid component, which includes Venusian electrons (e) and two types of positive ions,  H⁺and O⁺ . From this model, we derive the linear dispersion relation that governs the behavior of Langmuir mode, H⁺, and O⁺  ion acoustic modes. Our analysis reveals distinct characteristics of the Langmuir H⁺ and O⁺ ion-acoustic modes depending on the temperature and density ratio of the Venusian ionosphere. We notice that the Langmuir mode is not affected by pumping energy. The H⁺ and O⁺  ion acoustic modes are affected by pumping energy. As altitude increases within the Venusian ionosphere, the frequency of Langmuir mode H⁺ and O⁺ ion acoustic mode increases, but the frequency of O⁺ mode decreases. The findings provide insights into the dynamics of the Venusian ionosphere and an understanding of linear modes in extraterrestrial environments that have the same physical behavior.