Grey system theory regards uncertain system in which information is known partly and unknown partly as research object, extracts useful information from part known, and thereby revealing the potential variation rule of the system. In order to research the applicability of data-driven modelling method in melting peak temperature (Tm) fitting and prediction of polypropylene (PP) during ultraviolet radiation aging, the Tm of homo-polypropylene after different ultraviolet radiation exposure time investigated by differential scanning calorimeter was fitted and predicted by grey GM(1, 1) model based on grey system theory. The results show that the Tm of PP declines with the prolong of aging time, and fitting and prediction equation obtained by grey GM(1, 1) model is Tm = 166.567472exp(−0.00012t). Fitting effect of the above equation is excellent and the maximum relative error between prediction value and actual value of Tm is 0.32%. Grey system theory needs less original data, has high prediction accuracy, and can be used to predict aging behaviour of PP.