Antibacterial soap is the most popular soap in Indonesia as a cleaning agent. Unfortunately, antibacterial soap has some issues, such as the antibacterial ingredients used, and the soap form itself. Most of antibacterial ingredients used has been banned by the United States Food and Drug Administration (FDA) bacteria resistant to antibiotics. Therefore, we need safe antibacterial ingredients for both long and short term use. Microalgae Spirulina platensis is one of microalgae that contains safe antibacterial compound, such as phycocyanin. In addition, these types of microalgae have other compounds that are very beneficial for skin. This research aims to obtain the optimal saponification reaction temperature of VCO and microalgae Spirulina platensis based antibacterial soap. The alkaline used to make this soap was NaOH 6.25 M. The variation of reaction temperature used is 50, 60, and 70°C. Free alkali/free fatty acid content in soap was obtained by titrating soap solution using KOH or HCl depends on the characteristic of soap. Water content was obtained by gravimetric method. Meanwhile antibacterial activity was done in Jasa Pengujian dan Penelitian (QLab). Based on quality, soap that made of 70°C is the best sample with 13.09% (wt/wt) of water, 0.08% (wt/wt) of free alkali and minimum inhibitory value 0 or no bacteria growth until 25% of dilution.