Micro-silica in both types of powder and gel are used for improving the mechanical characteristics of the concrete. Sulfate attack is an important factor that influences on compressive strength and durability of concrete too. In this paper, 2.5%, 5%, 7.5%, 10%, 12.5% and 15% of cement weight is replaced by powder and gel of micro-silica. Then, the 7-day and 28-day compressive strengths of these specimens after curing in the sulfate (solution of sodium sulfate) and normal environments are evaluated. Accelerated sulfate environment was prepared by solution of 525 kg sodium sulfate in the water. 5 cubic specimens for each mix design layout and with dimensions of 15 x 15 x 15 centimeter were constructed and after curing in sulfate and normal conditions, the compressive strength of these specimens determined too. Results show that, using micro-silica (10% powder and gel) concludes to more compressive strength in the both normal and sulfate environments.