This paper presents an experimental study, including evaluation and modification, on using dehydrated cement paste (DCP) as a new type of cement additive. After a series of processes, normal DCP (N-DCP) was produced as before and a modified form of DCP (M-DCP) was produced as well. The cementitious characteristics of the groups with different kinds and contents of DCPs were evaluated by following/using the required water of standard consistency, setting times, and compressive strength development. A new concept-evaluating the strength contribution of DCPs by using the theoretical strength contribution (TSC)-is proposed in this paper. The experimental results show that N-DCP can be used as a new type of cement additive to artificially adjust the consistency, setting times, and compressive strength of cement. When the content of N-DCP is approximately 9.47%, the value of TSC can reach 20% after approximately 1 day. In addition, the M-DCP that was produced in this study can be used to maintain high requirements of compressive strength in practice. Comparing that value of the N-DCP/cement system, when the content of M-DCP is approximately 3.5%, the value of TSC can reach almost 40% at both early and later stages.