Recently, the development and field applications of Ternary Blended Cement(TBC), where blast furnace slag and fly ash are recycled in Ordinary Portland Cement(OPC) in order to obtain improvements in the durability and heat of hydration reduction performance in large scale civil structures, have been increasing. Also, there are continuing efforts by construction companies to reduce the construction time with the aim of reducing construction costs. Therefore, there is a need to improve the performance of TBC, which has a relatively slow early strength development. In order to improve the early strength of TBC mortar, the compressive strength, SO3 content, and SEM analysis was determined in this study on mortar with the fineness and content of blast furnace slag and anhydrite regulated. As a result, to secure the early strength of TBC mortar, using blast furnace slag with a fineness of approximately $4,200cm^2/g$, adding 3.5% anhydrite with a fineness of approximately $10,000cm^2/g$, and managing the $SO_3$ content to roughly 3.72% was found to provide the most outstanding early strength properties.