The linear and nonlinear optical properties of three porphyrin compounds with different substituents, meso-tetra (p-hydroxyphenyl) porphyrin ［T(4-HP)P］, meso-tetra (p-esterphenyl) porphyrin ［T(4-EP)P］ and meso-tetra (p-bromophenyl) porphyrin ［T(4-BrP)P］ have been investigated by using absorption spectroscopy, fluorescence spectroscopy and picosecond Z-scan technique. The optical properties of the three compounds were discussed on the basis of π-electron conjugated structures and resonant/non-resonant enhancement. The experimental results showed that the absorption and fluorescent emission bands of T(4-HP)P substituted by stronger donating electron group shift towards lower photon energy, in comparison of T(4-EP)P substituted by weaker donating electron group and T(4-BrP)P substituted by accepting electron group. All the three compounds had positive third-order nonlinear susceptibilities χ(3). With the resonant excitation at 532 nm, the third-order nonlinear susceptibility χ(3) of T(4-HP)P showed a maximum of 6.81×10-10 esu, which is two orders of magnitude larger than that of T(4-BrP)P.