Considering the fatigue life of electronic packages under thermal-cyclic loading, the real test outcome reflects the fatigue life of an electronic package is, in fact, not deterministic but a random variable following a certain probability distribution. The outcome has been paid attention to and become an important issue that needs to be investigated furthermore. Therefore, in the present study, a finite element analysis and a Monte Carlo simulation-based parametric study of a flip-chip chip scale package (FCCSP) subjected to thermal cyclic loading is carried out by using Probabilistic Design System (PDS) of ANSYS. In the first stage of the analysis, a few parameters involved in the package dimension, material property and life prediction formula are assumed to be random to account for their uncertainties. Moreover, to improve the accuracy of the probabilistic life distribution obtained from PDS, a refined probabilistic design procedure which includes probability paper and chi-square goodness-of-fit test is proposed in particular. In the second stage of the analysis, emphasis is placed on the confirmation of an acceleration model in which the accelerated thermal-cyclic tests are carried out numerically based on the analytical model established previously. The analytical result indicates that random geometric configuration, material property and random life prediction formula may cause fatigue life of the package to have scattered distribution as those observed from experiments. The result also indicates that PDS can indeed be employed to find the cumulative fatigue life distribution of the electronic package owing to parameter uncertainties, and the proposed refined procedure can further improve the smoothness of the cumulative fatigue life distribution curve and transform this curve into a closed form expression. Finally, a confirmed acceleration model can be used for the prediction of mean time to failure (MTTF), reliability and failure rate of the package under different thermal-cyclic conditions including the field or field-used one.