This theoretical study at the level PM3, has been to predict the more stable structure of bis (1,5-diphenyl-1,2,4-triazole-3-thionate) lead (II) (Pb(DTT) ), through the application of the 2 Pearson's Principle Maximum Hardness (PMH). 1 Proposed three possible structures which are reported by Angulo et al , to the based on experimental data. Determined that the structure presented greater hardness and thermodynamics stability is when lead atom is coordinated with the sulfur atom and the hydrazine nitrogen, in Ψbipiramide trigonal structure, coinciding this with the experimental data.