There has been researched on the optimization of fly ash Baturaja as a cement additive PCC. The purpose of this research is to know the optimal percentage of fly ash, which can be added to the process of making PCC cement, which still produces excellent quality cement and fulfills SNI and knowing the effect of adding fly ash to physical testing and chemical testing. The test was done physically, Blaine test, setting time test and compressive strength test for three days, seven days, and 28 days. Meanwhile, chemical testing is the Loss of Ignition (LOI) test, Free Calcium Oxide (FCaO) test, and Insoluble Residue test (IR). Based on the result of research, the most optimal percentage is when adding 6% ash fly proportion. The higher the ratio of fly ash, will result in an unstable Blaine value. The higher the proportion of fly ash is added, the compressive strength will be smaller, and the setting time will be longer. Meanwhile, the higher the addition of fly ash, the value of loss of ignition, Free Calcium Oxide, and insoluble residue value will be higher.