Corn stralk ash (CSA) is considered as one of the most recent abundant, renewable and green supplementary cementitious materials, which in turn is an effective approach to reduce the quantity of cement portion in blended cement. This in turn minimized the environmental pollution and also the CO2↑ emission. In the present study, the influence of CSA on the physical, chemical and mechanical properties as well as the microstructure of hydrated cement pastes containing various ratios of CSA up to 90 days was evaluated. Several techniques were carried out to confirm the obtained results of the newly formed hydration products as heat of hydration, and SEM images. It is concluded that the cement could be partially replaced by CSA without any adverse response on the properties of cement pastes. The SEM images showed that the content of the calcium dioxide or free lime is obviously decreased with CSA or may be disappeared.