Functional molecules of 5,10,15,20-tetraphenyl porphyrin manganese (MnTPP) and 5,10,15,20-tetraphenyl porphyrin indium (InTPP) were aggregated to be nano-materials in the water/ dimethylsulfoxide (DMSO) mixed solution by using mixed-solvents approach. UV-Vis method was used in this study, nano-dispersion systems were applied to detect dimethylmethylphosphonate (DMMP), which used to be simulant of sarin agent. Detection limits of MnTPP and InTPP to DMMP were 10-9 and 10-10 L/L respectively. Two reaction models between porphyrins and DMMP were constructed and optimized by using Density Functional Theory (DFT). The results indicated the sensing property to DMMP of InTPP was superior. This was consistent with detection results of UV-Vis technology.