Abstract: Using the self-developed diagenetic simulation system, the paper selects the medium-sized feldspar sandstone as the research object, and carries out diagenetic simulations on microscopic dissolution characteristics, soluble components, ion changes of diagenetic fluids and dissolution products of feldspar dissolution. The study shows that under the condition of acidic fluid, different types of feldspar have different degrees of dissolution and intense dissolution occurs to plagioclase, and its particle surface shows a harbor-shaped deep groove or dissolutions along the direction of the twin crystals. Dissolution mostly occurs at the edge or in the interior of the particles of potassium feldspar. The variations of the concentrations of K+, Na+, Ca2+, Mg2+, Al3+, Si4+ etc. reflect the status of feldspar dissolution, and the increase of the concentrations of K+, Na+ and Ca2+ indicate the acceleration of the dissolution rate of K-feldspar, albite and plagioclase. The concentration of K+ during the feldspar dissolution is relatively low and the ion is easy to be taken away rapidly, which result in the difficulties of K+ concentration required by illite deposition to be reached. Therefore, the authigenic clay minerals generated during the feldspar dissolution are mostly kaolinite. The changes of Mg2+ concentration may represent the dissolutions of carbonate and clay minerals at the late stage. Flow rate of acid fluid, temperature, surface area of feldspar grain and dissolution time are the key factors influencing feldspar dissolution