Cancer is the second largest cause of death in the world. There are cancer therapy commonly used such as surgery, radiation and chemotherapy, but many deficiencies are still found. One of cancer therapy that being develop is Photodynamic Therapy (PDT). PDT has a greater selectivity to destroy cancer cells since the cells are exposed to 3 main components namely photosensitizer (nontoxic drugs), light and oxygen together. The compound used a photosensitizer of macrocyclic tetrapyrole group namely Magnesium Phthalocyanine (MgPc) compound. The purpose of this study is to determine the physicochemical characteristics of MgPc compounds that determine their potential in PDT. In the prediction absorption, log P value of 3.81 which shows lipophilic compound. In the absorbance and molar absorptivity test the peak was obtained in the Q1 band at λ 670 nm with the result of molar absorption of 92.625 cm-1 M-1 which showed that the MgPc compound was effectively used for excitation of photosensitizer with lower concentrations and could be used for cancer therapy in tissues the deeper. The results of Δ indicate that 1O2 can be formed at pH 6.3 and pH 7.4 with results of 0.14 and 0.28. Then the F result, 1.0929, states that the MgPc compound can fluoresce. Also, the results of stability tests on indirect sunlight are unstable MgPc compounds (photodegradation). It can be concluded that the MgPc compound is thought to have more potential as a photosensitizer in PDT for the action of photodiagnosis of cancer cells.