Five porphyrin derivatives were synthesized and characterized in order to be utilized as photosensitizers for singlet oxygen generation. UV‐Vis absorption properties of porphyrins were experimentally and theoretically discussed. The results indicated that the increase in π‐conjugation of porphyrin core can lower the S1‐T1 energy gap and is favorable for efficient energy transfer. The singlet oxygen generation ability of porphyrins was measured and compared under both simulated sunlight and yellow light. As for the results using simulated sunlight, EBHPP and CEBHPP exhibited best and similar performance because they bear strong near‐IR absorption and S1‐T1 interactions. However, under yellow light conditions CEBHPP has better ability for singlet oxygen generation because of its strong absorbance from 650–750 nm. The DNA photocleavage measurements were performed to evaluate the biological activity of the porphyrin derivatives. The photocleavage activities were in the order of TPP < TPP‐NO2 < BHPP < EBHPP < CEBHPP, and the possible reasons were discussed. This work is useful for the design of more efficient photosensitizers.