<p>This paper presents a computational analysis of two-diffusive convection in 3D pyramid solar still using conductive fins. The study explores heat and mass transmission inside the solar still, focusing on the influences of buoyancy ratio, Rayleigh number and fin conductivity. Using COMSOL Multiphysics software, a three-dimensional diffusive double convection model is developed. The analysis reveals the significant impact of fin conductivity on isotherms and iso-concentration, emphasizing enhanced convective heat transfer with increasing fin conductivity. The findings provide valuable insights for improving solar still systems through material and buoyancy adjustments. The study underscores the critical role of buoyancy in shaping both convective heat and mass transfer characteristics, with optimal performance observed at negligible buoyancy and high fin conductivity.</p>