By comparing the global modeling method of electric loads with the node modeling method， it can be concluded that the parameter accuracy of the global modeling method is a little better than that of the node modeling method， but the computing workload is much greater. Based on a comparison between three different error indices， the results show that they have roughly the same parameter accuracy， while the index of trajectory error squares behaves tolerably well. Then， three kinds of measurement variables are compared. The example shows that the sensitivity decreases with the relative generator angle， tie line power and key bus voltage. It has been found that the greater the sensitivity is， the higher will the accuracy be.