ABSTRACT This study project presents of an experimental investigation carried out to evaluate effects of replacing cement with metakaolin clay. The properties of metakaolin are very similar to the cement properties. Metakaolin is also a mineral admixture which converts calcium hydroxide into advantageous cementitious material. The use of supplementary cementitious material in production of concrete can result in major saving of energy and cost. It also helps to improve strength, durability, impermeability and chemical resistance of concrete. The present study investigates the effects of Metakaolin clay on strength properties of M30 grade concrete. The experimental program is designed to find the compressive strength of concrete by partially replacing the cement in concrete production. The replacement levels of cement by metakaolin are selected as 10%, 20%, and 30% for constant water-cementitious material ratio. For all mixes compressive strength is determined at 7, 14, 28 days for 150 X 150 X 150 mm size cubes. And we cast cubes at various percentages of replacements and we can find the optimum percentage metakaolin clay in concrete. Keywords: Investigation, Concrete, Replacing, Cement, Metakaolin Clay.