Optimal placement of DG based on traditional sensitivity analysis may lead to improper location layout and inaccurate location selection. Through setting up a second-order model, the nonlinear relationship between objective function and sizing of DG is presented. Instead of traditional first-order sensitivity, a new potentiality index is used to guide DG location selection. Through applying self-adaptive catastrophic genetic algorithms into the IEEE15-bus system as an example, the optimization results of all configurations are compared. The results demonstrate the effectiveness of the proposed method on improving power loss and voltage quality.