Based on MATLAB software and iterative method, a kind of trial-error method for different natural environments (NET) is proposed. Solar module temperature, solar radiation and their effects on series resistance are taken into account in this model. Nine I-V curves are measured under natural environmental conditions to predict the model parameters under STC (i.e. open voltage Vocrefi, short current Iscrefi, maximum voltage Vmrefi, maximum current Imrefi, maximum power Pmrefi,i=1~7) . Increasing the number of the measured I-V curves may help for obtaining more accurate real value of Vocref, Iscref, Vmref, Imref, Pmref under STC. In order to test the validation of this model, the proposed model is used to evaluate the solar energy output of the module under a condition except for the nine I-V curves with nine different natural conditions. The deviation of the output of the calculated PmC from the measured output PmE under the investigated condition (G=647 W/m2, T=67.7℃) turns out to be 2.73%, which means that this kind of trial-error model can be used to design PV modules and predict the yield of the module under arbitrary natural environment.